fix(Microsoft Outlook Node): Resolve service principal mailbox per input item (#34110)

.boundaries-baseline.json

@@ -1,3 +1,3 @@
 {
-  "issues": 558
+  "issues": 561
 }

packages/nodes-base/nodes/Microsoft/Outlook/test/trigger/GenericFunctions.test.ts

@@ -96,7 +96,7 @@ describe('Microsoft Outlook Trigger GenericFunctions', () => {
 				it('should handle simple output format in manual mode', async () => {
 					const result = await getPollResponse.call(mockPollFunctions, pollStartDate, pollEndDate);
 
-					expect(microsoftApiRequest).toHaveBeenCalledWith('GET', '/messages', undefined, {
+					expect(microsoftApiRequest).toHaveBeenCalledWith('GET', '/messages', 0, undefined, {
 						$select:
 							'id,conversationId,subject,bodyPreview,from,toRecipients,categories,hasAttachments',
 						$top: 1,
@@ -122,7 +122,7 @@ describe('Microsoft Outlook Trigger GenericFunctions', () => {
 
 					const result = await getPollResponse.call(mockPollFunctions, pollStartDate, pollEndDate);
 
-					expect(microsoftApiRequest).toHaveBeenCalledWith('GET', '/messages', undefined, {
+					expect(microsoftApiRequest).toHaveBeenCalledWith('GET', '/messages', 0, undefined, {
 						$select: 'id,subject,from',
 						$top: 1,
 					});
@@ -152,11 +152,11 @@ describe('Microsoft Outlook Trigger GenericFunctions', () => {
 
 					const result = await getPollResponse.call(mockPollFunctions, pollStartDate, pollEndDate);
 
-					expect(microsoftApiRequest).toHaveBeenCalledWith('GET', '/messages', undefined, {
+					expect(microsoftApiRequest).toHaveBeenCalledWith('GET', '/messages', 0, undefined, {
 						$select: 'id,subject,from,hasAttachments',
 						$top: 1,
 					});
-					expect(downloadAttachments).toHaveBeenCalledWith([mockMessages[0]], 'attachment_');
+					expect(downloadAttachments).toHaveBeenCalledWith([mockMessages[0]], 'attachment_', 0);
 					expect(result).toEqual(mockExecutionData);
 				});
 			});
@@ -174,6 +174,7 @@ describe('Microsoft Outlook Trigger GenericFunctions', () => {
 						'value',
 						'GET',
 						'/messages',
+						0,
 						undefined,
 						{
 							$select:
@@ -204,6 +205,7 @@ describe('Microsoft Outlook Trigger GenericFunctions', () => {
 						'value',
 						'GET',
 						'/messages',
+						0,
 						undefined,
 						{
 							$select: 'id,subject,receivedDateTime',
@@ -224,6 +226,7 @@ describe('Microsoft Outlook Trigger GenericFunctions', () => {
 						'value',
 						'GET',
 						'/messages',
+						0,
 						undefined,
 						{
 							$select:
@@ -255,7 +258,7 @@ describe('Microsoft Outlook Trigger GenericFunctions', () => {
 
 					const result = await getPollResponse.call(mockPollFunctions, pollStartDate, pollEndDate);
 
-					expect(downloadAttachments).toHaveBeenCalledWith(mockMessages, 'custom_');
+					expect(downloadAttachments).toHaveBeenCalledWith(mockMessages, 'custom_', 0);
 					expect(result).toEqual(mockExecutionData);
 				});
 
@@ -281,7 +284,7 @@ describe('Microsoft Outlook Trigger GenericFunctions', () => {
 
 					await getPollResponse.call(mockPollFunctions, pollStartDate, pollEndDate);
 
-					expect(downloadAttachments).toHaveBeenCalledWith(mockMessages, 'attachment_');
+					expect(downloadAttachments).toHaveBeenCalledWith(mockMessages, 'attachment_', 0);
 				});
 			});
 
@@ -313,6 +316,7 @@ describe('Microsoft Outlook Trigger GenericFunctions', () => {
 							'value',
 							'GET',
 							`/mailFolders/${folderId1}/messages`,
+							0,
 							undefined,
 							{
 								$select:
@@ -352,6 +356,7 @@ describe('Microsoft Outlook Trigger GenericFunctions', () => {
 							'value',
 							'GET',
 							`/mailFolders/${folderId1}/messages`,
+							0,
 							undefined,
 							expect.objectContaining({ $filter: expect.any(String) }),
 						);
@@ -359,6 +364,7 @@ describe('Microsoft Outlook Trigger GenericFunctions', () => {
 							'value',
 							'GET',
 							`/mailFolders/${folderId2}/messages`,
+							0,
 							undefined,
 							expect.objectContaining({ $filter: expect.any(String) }),
 						);
@@ -402,6 +408,7 @@ describe('Microsoft Outlook Trigger GenericFunctions', () => {
 							'value',
 							'GET',
 							'/messages',
+							0,
 							undefined,
 							expect.objectContaining({ $filter: expect.any(String) }),
 						);
@@ -432,6 +439,7 @@ describe('Microsoft Outlook Trigger GenericFunctions', () => {
 						expect(microsoftApiRequest).toHaveBeenCalledWith(
 							'GET',
 							`/mailFolders/${folderId1}/messages`,
+							0,
 							undefined,
 							{
 								$select:
@@ -442,6 +450,7 @@ describe('Microsoft Outlook Trigger GenericFunctions', () => {
 						expect(microsoftApiRequest).toHaveBeenCalledWith(
 							'GET',
 							`/mailFolders/${folderId2}/messages`,
+							0,
 							undefined,
 							{
 								$select:
@@ -500,7 +509,7 @@ describe('Microsoft Outlook Trigger GenericFunctions', () => {
 
 					const result = await getPollResponse.call(mockPollFunctions, pollStartDate, pollEndDate);
 
-					expect(microsoftApiRequest).toHaveBeenCalledWith('GET', '/messages', undefined, {
+					expect(microsoftApiRequest).toHaveBeenCalledWith('GET', '/messages', 0, undefined, {
 						$top: 1,
 					});
 					expect(simplifyOutputMessages).not.toHaveBeenCalled();
@@ -550,7 +559,7 @@ describe('Microsoft Outlook Trigger GenericFunctions', () => {
 
 					await getPollResponse.call(mockPollFunctions, pollStartDate, pollEndDate);
 
-					expect(microsoftApiRequest).toHaveBeenCalledWith('GET', '/messages', undefined, {
+					expect(microsoftApiRequest).toHaveBeenCalledWith('GET', '/messages', 0, undefined, {
 						$select: 'id,subject,hasAttachments',
 						$top: 1,
 					});
@@ -719,7 +728,7 @@ describe('Microsoft Outlook Trigger GenericFunctions', () => {
 
 				const result = await getPollResponse.call(mockPollFunctions, pollStartDate, pollEndDate);
 
-				expect(microsoftApiRequest).toHaveBeenCalledWith('GET', '/messages', undefined, {
+				expect(microsoftApiRequest).toHaveBeenCalledWith('GET', '/messages', 0, undefined, {
 					$select: '',
 					$top: 1,
 				});
@@ -754,6 +763,7 @@ describe('Microsoft Outlook Trigger GenericFunctions', () => {
 					'value',
 					'GET',
 					'/messages',
+					0,
 					undefined,
 					{
 						$select: 'id,subject,from,isRead',
@@ -792,13 +802,14 @@ describe('Microsoft Outlook Trigger GenericFunctions', () => {
 					'value',
 					'GET',
 					'/messages',
+					0,
 					undefined,
 					{
 						$select: 'id,subject,hasAttachments',
 						$filter: `isRead eq false and receivedDateTime ge ${pollStartDate} and receivedDateTime lt ${pollEndDate}`,
 					},
 				);
-				expect(downloadAttachments).toHaveBeenCalledWith(mockMessages, 'prefix_');
+				expect(downloadAttachments).toHaveBeenCalledWith(mockMessages, 'prefix_', 0);
 				expect(result).toEqual(mockExecutionData);
 			});
 		});

packages/nodes-base/nodes/Microsoft/Outlook/test/v2/actions/router.test.ts

@@ -0,0 +1,53 @@
+import type { IExecuteFunctions, INode } from 'n8n-workflow';
+import { NodeOperationError } from 'n8n-workflow';
+import type { Mock, Mocked } from 'vitest';
+import { mockDeep } from 'vitest-mock-extended';
+
+import { router } from '../../../v2/actions/router';
+
+describe('MicrosoftOutlookV2 - router error attribution', () => {
+	it('stamps context.itemIndex on a NodeError from the failing item', async () => {
+		const mockExecuteFunctions: Mocked<IExecuteFunctions> = mockDeep<IExecuteFunctions>();
+		const mockNode: INode = {
+			id: 'test-node',
+			name: 'Test Outlook Node',
+			type: 'n8n-nodes-base.microsoftOutlook',
+			typeVersion: 2,
+			position: [0, 0],
+			parameters: {},
+		};
+		mockExecuteFunctions.getNode.mockReturnValue(mockNode);
+		mockExecuteFunctions.getInputData.mockReturnValue([{ json: {} }, { json: {} }]);
+		mockExecuteFunctions.continueOnFail.mockReturnValue(false);
+		mockExecuteFunctions.getCredentials.mockResolvedValue({
+			accessToken: 'test-access-token',
+			graphApiBaseUrl: '',
+		});
+		mockExecuteFunctions.helpers.requestWithAuthentication = vi.fn().mockResolvedValue({});
+		(mockExecuteFunctions.helpers.constructExecutionMetaData as Mock).mockReturnValue([]);
+		// message:delete on two items: item 0's mailbox is valid, item 1's is not — the
+		// unstamped validator error must leave the router carrying item 1's index.
+		mockExecuteFunctions.getNodeParameter.mockImplementation((name, itemIndex, fallback) => {
+			const params: Record<string, unknown> = {
+				resource: 'message',
+				operation: 'delete',
+				authentication: 'microsoftEntraServicePrincipalApi',
+				messageId: 'MSG1',
+			};
+			if (name === 'mailbox')
+				return (itemIndex === 1 ? 'contoso.com' : '[email protected]') as never;
+			return (name in params ? params[name] : fallback) as never;
+		});
+
+		let caught: unknown;
+		try {
+			await router.call(mockExecuteFunctions);
+		} catch (error) {
+			caught = error;
+		}
+
+		expect(caught).toBeInstanceOf(NodeOperationError);
+		expect((caught as NodeOperationError).message).toBe('The mailbox is not valid');
+		expect((caught as NodeOperationError).context.itemIndex).toBe(1);
+	});
+});

packages/nodes-base/nodes/Microsoft/Outlook/test/v2/methods/listSearch.test.ts

@@ -49,6 +49,7 @@ describe('MicrosoftOutlookV2 - listSearch methods', () => {
 			expect(mockTransport.microsoftApiRequest).toHaveBeenCalledWith(
 				'GET',
 				'/contacts',
+				0,
 				undefined,
 				{
 					$select: 'id,displayName',
@@ -76,6 +77,7 @@ describe('MicrosoftOutlookV2 - listSearch methods', () => {
 			expect(mockTransport.microsoftApiRequest).toHaveBeenCalledWith(
 				'GET',
 				'/contacts',
+				0,
 				undefined,
 				{
 					$select: 'id,displayName',
@@ -102,6 +104,7 @@ describe('MicrosoftOutlookV2 - listSearch methods', () => {
 			expect(mockTransport.microsoftApiRequest).toHaveBeenCalledWith(
 				'GET',
 				'',
+				0,
 				undefined,
 				undefined,
 				paginationToken,
@@ -125,6 +128,7 @@ describe('MicrosoftOutlookV2 - listSearch methods', () => {
 			expect(mockTransport.microsoftApiRequest).toHaveBeenCalledWith(
 				'GET',
 				'/calendars',
+				0,
 				undefined,
 				{
 					$select: 'id,name',
@@ -161,6 +165,7 @@ describe('MicrosoftOutlookV2 - listSearch methods', () => {
 			expect(mockTransport.microsoftApiRequest).toHaveBeenCalledWith(
 				'GET',
 				'/messages',
+				0,
 				undefined,
 				{
 					$select: 'id,subject,bodyPreview,webLink',
@@ -199,6 +204,7 @@ describe('MicrosoftOutlookV2 - listSearch methods', () => {
 			expect(mockTransport.microsoftApiRequest).toHaveBeenCalledWith(
 				'GET',
 				'/messages',
+				0,
 				undefined,
 				{
 					$select: 'id,subject,bodyPreview,webLink',
@@ -248,6 +254,7 @@ describe('MicrosoftOutlookV2 - listSearch methods', () => {
 			expect(mockTransport.microsoftApiRequest).toHaveBeenCalledWith(
 				'GET',
 				'/messages',
+				0,
 				undefined,
 				{
 					$select: 'id,subject,bodyPreview,webLink',
@@ -285,6 +292,7 @@ describe('MicrosoftOutlookV2 - listSearch methods', () => {
 			expect(mockTransport.microsoftApiRequest).toHaveBeenCalledWith(
 				'GET',
 				'/messages',
+				0,
 				undefined,
 				{
 					$select: 'id,subject,bodyPreview,webLink',
@@ -327,6 +335,7 @@ describe('MicrosoftOutlookV2 - listSearch methods', () => {
 			expect(mockTransport.microsoftApiRequest).toHaveBeenCalledWith(
 				'GET',
 				`/calendars/${calendarId}/events`,
+				0,
 				undefined,
 				{
 					$select: 'id,subject,bodyPreview',
@@ -365,6 +374,7 @@ describe('MicrosoftOutlookV2 - listSearch methods', () => {
 			expect(mockTransport.microsoftApiRequest).toHaveBeenCalledWith(
 				'GET',
 				`/calendars/${calendarId}/events`,
+				0,
 				undefined,
 				{
 					$select: 'id,subject,bodyPreview',
@@ -401,12 +411,13 @@ describe('MicrosoftOutlookV2 - listSearch methods', () => {
 			expect(mockTransport.microsoftApiRequest).toHaveBeenCalledWith(
 				'GET',
 				'/mailFolders',
+				0,
 				undefined,
 				{
 					$top: 100,
 				},
 			);
-			expect(mockTransport.getSubfolders).toHaveBeenCalledWith(mockResponse.value, true);
+			expect(mockTransport.getSubfolders).toHaveBeenCalledWith(mockResponse.value, 0, true);
 			expect(result).toEqual({
 				results: [
 					{
@@ -506,6 +517,7 @@ describe('MicrosoftOutlookV2 - listSearch methods', () => {
 			expect(mockTransport.microsoftApiRequest).toHaveBeenCalledWith(
 				'GET',
 				`/messages/${messageId}/attachments`,
+				0,
 				undefined,
 				{
 					$select: 'id,name',
@@ -537,6 +549,7 @@ describe('MicrosoftOutlookV2 - listSearch methods', () => {
 			expect(mockTransport.microsoftApiRequest).toHaveBeenCalledWith(
 				'GET',
 				'',
+				0,
 				undefined,
 				undefined,
 				paginationToken,

packages/nodes-base/nodes/Microsoft/Outlook/test/v2/methods/loadOptions.test.ts

@@ -37,6 +37,7 @@ describe('MicrosoftOutlookV2 - loadOptions methods', () => {
 				'value',
 				'GET',
 				'/outlook/masterCategories',
+				0,
 			);
 			expect(result).toEqual([
 				{ name: 'Red Category', value: 'Red Category' },
@@ -125,9 +126,10 @@ describe('MicrosoftOutlookV2 - loadOptions methods', () => {
 				'value',
 				'GET',
 				'/mailFolders',
+				0,
 				{},
 			);
-			expect(mockTransport.getSubfolders).toHaveBeenCalledWith(mockResponse, true);
+			expect(mockTransport.getSubfolders).toHaveBeenCalledWith(mockResponse, 0, true);
 			expect(result).toEqual([
 				{ name: 'Inbox', value: 'folder1' },
 				{ name: 'Sent Items', value: 'folder2' },
@@ -222,6 +224,7 @@ describe('MicrosoftOutlookV2 - loadOptions methods', () => {
 				'value',
 				'GET',
 				'/calendarGroups',
+				0,
 				{},
 			);
 			expect(result).toEqual([

packages/nodes-base/nodes/Microsoft/Outlook/test/v2/node/draft/create.test.ts

@@ -190,6 +190,7 @@ describe('Test MicrosoftOutlookV2, draft => create', () => {
 			expect(microsoftApiRequestSpy).toHaveBeenCalledWith(
 				'POST',
 				'/messages',
+				0,
 				expect.objectContaining({
 					subject: 'Test Draft with Attachment',
 					body: expect.objectContaining({
@@ -243,11 +244,14 @@ describe('Test MicrosoftOutlookV2, draft => create', () => {
 
 			microsoftApiRequestSpy.mockResolvedValue({});
 
-			await execute.call(mockExecuteFunctions, 0, [{ json: {} }]);
+			// Non-zero index: pins that the operation forwards the PASSED index (not a
+			// hardcoded 0). The getNodeParameter mock is index-insensitive.
+			await execute.call(mockExecuteFunctions, 2, [{ json: {} }]);
 
 			expect(microsoftApiRequestSpy).toHaveBeenCalledWith(
 				'POST',
 				'/messages',
+				2,
 				expect.objectContaining({
 					attachments: [
 						{
@@ -296,6 +300,7 @@ describe('Test MicrosoftOutlookV2, draft => create', () => {
 			expect(microsoftApiRequestSpy).toHaveBeenCalledWith(
 				'POST',
 				'/messages',
+				0,
 				expect.objectContaining({
 					attachments: expect.arrayContaining([
 						expect.objectContaining({

packages/nodes-base/nodes/Microsoft/Outlook/test/v2/node/message/sendAndWait.test.ts

@@ -64,7 +64,7 @@ describe('Test MicrosoftOutlookV2, message => sendAndWait', () => {
 		expect(transport.microsoftApiRequest).toHaveBeenCalledTimes(1);
 		expect(mockExecuteFunctions.putExecutionToWait).toHaveBeenCalledTimes(1);
 
-		expect(transport.microsoftApiRequest).toHaveBeenCalledWith('POST', '/sendMail', {
+		expect(transport.microsoftApiRequest).toHaveBeenCalledWith('POST', '/sendMail', 0, {
 			message: {
 				body: {
 					content: expect.stringContaining(

packages/nodes-base/nodes/Microsoft/Outlook/test/v2/node/messageAttachment/add.test.ts

@@ -90,6 +90,7 @@ describe('Microsoft Outlook V2 - MessageAttachment:add', () => {
 			expect(microsoftApiRequestSpy).toHaveBeenCalledWith(
 				'POST',
 				'/messages/AAMkAGI2TG93AAA=/attachments',
+				0,
 				{
 					'@odata.type': '#microsoft.graph.fileAttachment',
 					name: 'test-file.txt',
@@ -132,11 +133,14 @@ describe('Microsoft Outlook V2 - MessageAttachment:add', () => {
 
 			microsoftApiRequestSpy.mockResolvedValue({});
 
-			await execute.call(mockExecuteFunctions, 0, [{ json: {} }]);
+			// Non-zero index: pins that the operation forwards the PASSED index (not a
+			// hardcoded 0). The getNodeParameter mock is index-insensitive.
+			await execute.call(mockExecuteFunctions, 2, [{ json: {} }]);
 
 			expect(microsoftApiRequestSpy).toHaveBeenCalledWith(
 				'POST',
 				'/messages/AAMkAGI2TG93AAA=/attachments',
+				2,
 				{
 					'@odata.type': '#microsoft.graph.fileAttachment',
 					name: 'custom-name.pdf',
@@ -222,6 +226,7 @@ describe('Microsoft Outlook V2 - MessageAttachment:add', () => {
 			expect(microsoftApiRequestSpy).toHaveBeenCalledWith(
 				'POST',
 				'/messages/AAMkAGI2TG93BBB=/attachments/createUploadSession',
+				0,
 				{
 					AttachmentItem: {
 						attachmentType: 'file',

packages/nodes-base/nodes/Microsoft/Outlook/test/v2/node/servicePrincipal/folderGetAllPerItem.test.ts

@@ -0,0 +1,62 @@
+import { NodeTestHarness } from '@nodes-testing/node-test-harness';
+import nock from 'nock';
+
+// folder:getAll with includeChildFolders exercises the helper chain end-to-end:
+// operation -> microsoftApiRequest AND getSubfolders -> microsoftApiRequestAllItems ->
+// (recursive) getSubfolders. Fanning out to two mailboxes proves the loop index is
+// threaded through every hop — the child-folder fetch for item i's parent list must hit
+// item i's mailbox, not item 0's (which would cross-mix mailboxes). Consume-once
+// interceptors + empty pendingMocks pin the exact request set.
+describe('Test MicrosoftOutlookV2, Service Principal => folder:getAll per-item mailbox', () => {
+	const credentials = {
+		microsoftEntraServicePrincipalApi: {
+			accessToken: 'test-access-token',
+			tenantId: '11111111-1111-1111-1111-111111111111',
+			clientId: '22222222-2222-2222-2222-222222222222',
+			clientSecret: 'secret',
+			graphApiBaseUrl: 'https://graph.microsoft.com',
+		},
+	};
+
+	beforeAll(() => {
+		nock('https://graph.microsoft.com')
+			.matchHeader('Authorization', 'Bearer test-access-token')
+			.get('/v1.0/users/usera%40example.com/mailFolders')
+			.query({ $top: 50 })
+			.reply(200, {
+				value: [{ id: 'folder-a', displayName: 'Inbox A', childFolderCount: 1 }],
+			});
+
+		// childFolderCount > 0 makes getSubfolders recurse into this folder — the child
+		// fetch must stay on mailbox A.
+		nock('https://graph.microsoft.com')
+			.matchHeader('Authorization', 'Bearer test-access-token')
+			.get('/v1.0/users/usera%40example.com/mailFolders/folder-a/childFolders')
+			.query({ $top: 100 })
+			.reply(200, {
+				value: [{ id: 'sub-a', displayName: 'Sub A', childFolderCount: 0 }],
+			});
+
+		nock('https://graph.microsoft.com')
+			.matchHeader('Authorization', 'Bearer test-access-token')
+			.get('/v1.0/users/userb%40example.com/mailFolders')
+			.query({ $top: 50 })
+			.reply(200, {
+				value: [{ id: 'folder-b', displayName: 'Inbox B', childFolderCount: 1 }],
+			});
+
+		nock('https://graph.microsoft.com')
+			.matchHeader('Authorization', 'Bearer test-access-token')
+			.get('/v1.0/users/userb%40example.com/mailFolders/folder-b/childFolders')
+			.query({ $top: 100 })
+			.reply(200, {
+				value: [{ id: 'sub-b', displayName: 'Sub B', childFolderCount: 0 }],
+			});
+	});
+
+	new NodeTestHarness().setupTests({
+		credentials,
+		workflowFiles: ['folderGetAllPerItem.workflow.json'],
+		customAssertions: () => expect(nock.pendingMocks()).toEqual([]),
+	});
+});

packages/nodes-base/nodes/Microsoft/Outlook/test/v2/node/servicePrincipal/folderGetAllPerItem.workflow.json

@@ -0,0 +1,113 @@
+{
+	"name": "Microsoft Outlook Service Principal Folder Get All Per Item",
+	"nodes": [
+		{
+			"parameters": {},
+			"id": "e524f588-b6a3-4849-8777-b32a8a755af0",
+			"name": "When clicking \"Execute Workflow\"",
+			"type": "n8n-nodes-base.manualTrigger",
+			"typeVersion": 1,
+			"position": [820, 360]
+		},
+		{
+			"parameters": {
+				"data": [{ "mailbox": "[email protected]" }, { "mailbox": "[email protected]" }]
+			},
+			"id": "e524f588-b6a3-4849-8777-b32a8a755af1",
+			"name": "Test Data",
+			"type": "n8n-nodes-testing.testData",
+			"typeVersion": 1,
+			"position": [930, 360]
+		},
+		{
+			"parameters": {
+				"authentication": "microsoftEntraServicePrincipalApi",
+				"mailbox": {
+					"__rl": true,
+					"mode": "id",
+					"value": "={{ $json.mailbox }}"
+				},
+				"resource": "folder",
+				"operation": "getAll",
+				"returnAll": false,
+				"limit": 50,
+				"filters": {},
+				"options": {
+					"includeChildFolders": true
+				}
+			},
+			"id": "baff6798-0304-4255-bdb0-dd3f2659373d",
+			"name": "Microsoft Outlook",
+			"type": "n8n-nodes-base.microsoftOutlook",
+			"typeVersion": 2,
+			"position": [1040, 360],
+			"credentials": {
+				"microsoftEntraServicePrincipalApi": {
+					"id": "spCredId1",
+					"name": "Microsoft Entra Service Principal Test"
+				}
+			}
+		}
+	],
+	"pinData": {
+		"Microsoft Outlook": [
+			{
+				"json": {
+					"id": "folder-a",
+					"displayName": "Inbox A",
+					"childFolderCount": 1
+				}
+			},
+			{
+				"json": {
+					"id": "sub-a",
+					"displayName": "Sub A",
+					"childFolderCount": 0
+				}
+			},
+			{
+				"json": {
+					"id": "folder-b",
+					"displayName": "Inbox B",
+					"childFolderCount": 1
+				}
+			},
+			{
+				"json": {
+					"id": "sub-b",
+					"displayName": "Sub B",
+					"childFolderCount": 0
+				}
+			}
+		]
+	},
+	"connections": {
+		"When clicking \"Execute Workflow\"": {
+			"main": [
+				[
+					{
+						"node": "Test Data",
+						"type": "main",
+						"index": 0
+					}
+				]
+			]
+		},
+		"Test Data": {
+			"main": [
+				[
+					{
+						"node": "Microsoft Outlook",
+						"type": "main",
+						"index": 0
+					}
+				]
+			]
+		}
+	},
+	"active": false,
+	"settings": {
+		"executionOrder": "v1"
+	},
+	"tags": []
+}

packages/nodes-base/nodes/Microsoft/Outlook/test/v2/node/servicePrincipal/sendPerItem.test.ts

@@ -0,0 +1,45 @@
+import { NodeTestHarness } from '@nodes-testing/node-test-harness';
+import nock from 'nock';
+
+// The mailbox RLC accepts expressions, so it must be resolved per input item: a fan-out
+// to two mailboxes must produce one /users/{encoded-mailbox}/sendMail POST per mailbox.
+// Both interceptors are consume-once and `pendingMocks` must be empty afterwards, so a
+// run that sends both items from item 0's mailbox fails in either direction.
+describe('Test MicrosoftOutlookV2, Service Principal => message:send per-item mailbox', () => {
+	const credentials = {
+		microsoftEntraServicePrincipalApi: {
+			accessToken: 'test-access-token',
+			tenantId: '11111111-1111-1111-1111-111111111111',
+			clientId: '22222222-2222-2222-2222-222222222222',
+			clientSecret: 'secret',
+			graphApiBaseUrl: 'https://graph.microsoft.com',
+		},
+	};
+
+	const expectedBody = {
+		message: {
+			body: { content: 'message description', contentType: 'Text' },
+			subject: 'Hello',
+			toRecipients: [{ emailAddress: { address: '[email protected]' } }],
+		},
+		saveToSentItems: true,
+	};
+
+	beforeAll(() => {
+		nock('https://graph.microsoft.com')
+			.matchHeader('Authorization', 'Bearer test-access-token')
+			.post('/v1.0/users/alice%40example.com/sendMail', expectedBody)
+			.reply(200, {});
+
+		nock('https://graph.microsoft.com')
+			.matchHeader('Authorization', 'Bearer test-access-token')
+			.post('/v1.0/users/bob%40example.com/sendMail', expectedBody)
+			.reply(200, {});
+	});
+
+	new NodeTestHarness().setupTests({
+		credentials,
+		workflowFiles: ['sendPerItem.workflow.json'],
+		customAssertions: () => expect(nock.pendingMocks()).toEqual([]),
+	});
+});

packages/nodes-base/nodes/Microsoft/Outlook/test/v2/node/servicePrincipal/sendPerItem.workflow.json

@@ -0,0 +1,95 @@
+{
+	"name": "Microsoft Outlook Service Principal Message Send Per Item",
+	"nodes": [
+		{
+			"parameters": {},
+			"id": "e524f588-b6a3-4849-8777-b32a8a755ae6",
+			"name": "When clicking \"Execute Workflow\"",
+			"type": "n8n-nodes-base.manualTrigger",
+			"typeVersion": 1,
+			"position": [820, 360]
+		},
+		{
+			"parameters": {
+				"data": [{ "mailbox": "[email protected]" }, { "mailbox": "[email protected]" }]
+			},
+			"id": "e524f588-b6a3-4849-8777-b32a8a755ae7",
+			"name": "Test Data",
+			"type": "n8n-nodes-testing.testData",
+			"typeVersion": 1,
+			"position": [930, 360]
+		},
+		{
+			"parameters": {
+				"authentication": "microsoftEntraServicePrincipalApi",
+				"mailbox": {
+					"__rl": true,
+					"mode": "id",
+					"value": "={{ $json.mailbox }}"
+				},
+				"resource": "message",
+				"operation": "send",
+				"toRecipients": "[email protected]",
+				"subject": "Hello",
+				"bodyContent": "message description",
+				"additionalFields": {
+					"bodyContentType": "Text"
+				}
+			},
+			"id": "baff6798-0304-4255-bdb0-dd3f2659373c",
+			"name": "Microsoft Outlook",
+			"type": "n8n-nodes-base.microsoftOutlook",
+			"typeVersion": 2,
+			"position": [1040, 360],
+			"credentials": {
+				"microsoftEntraServicePrincipalApi": {
+					"id": "spCredId1",
+					"name": "Microsoft Entra Service Principal Test"
+				}
+			}
+		}
+	],
+	"pinData": {
+		"Microsoft Outlook": [
+			{
+				"json": {
+					"success": true
+				}
+			},
+			{
+				"json": {
+					"success": true
+				}
+			}
+		]
+	},
+	"connections": {
+		"When clicking \"Execute Workflow\"": {
+			"main": [
+				[
+					{
+						"node": "Test Data",
+						"type": "main",
+						"index": 0
+					}
+				]
+			]
+		},
+		"Test Data": {
+			"main": [
+				[
+					{
+						"node": "Microsoft Outlook",
+						"type": "main",
+						"index": 0
+					}
+				]
+			]
+		}
+	},
+	"active": false,
+	"settings": {
+		"executionOrder": "v1"
+	},
+	"tags": []
+}

packages/nodes-base/nodes/Microsoft/Outlook/test/v2/node/servicePrincipal/sendPerItemContinueOnFail.test.ts

@@ -0,0 +1,37 @@
+import { NodeTestHarness } from '@nodes-testing/node-test-harness';
+import nock from 'nock';
+
+// Per-item error isolation under continueOnFail: item 0's bogus mailbox ("contoso.com"
+// is a bare host, not a GUID/UPN) must route through the router's continueOnFail branch
+// as an error item for item 0 only, while items 1 and 2 still send from their own
+// mailboxes. Only the two valid mailboxes are mocked; consume-once + empty pendingMocks
+// pin the exact request set.
+describe('Test MicrosoftOutlookV2, Service Principal => message:send fails only the bad item under continueOnFail', () => {
+	const credentials = {
+		microsoftEntraServicePrincipalApi: {
+			accessToken: 'test-access-token',
+			tenantId: '11111111-1111-1111-1111-111111111111',
+			clientId: '22222222-2222-2222-2222-222222222222',
+			clientSecret: 'secret',
+			graphApiBaseUrl: 'https://graph.microsoft.com',
+		},
+	};
+
+	beforeAll(() => {
+		nock('https://graph.microsoft.com')
+			.matchHeader('Authorization', 'Bearer test-access-token')
+			.post('/v1.0/users/alice%40example.com/sendMail')
+			.reply(200, {});
+
+		nock('https://graph.microsoft.com')
+			.matchHeader('Authorization', 'Bearer test-access-token')
+			.post('/v1.0/users/bob%40example.com/sendMail')
+			.reply(200, {});
+	});
+
+	new NodeTestHarness().setupTests({
+		credentials,
+		workflowFiles: ['sendPerItemContinueOnFail.workflow.json'],
+		customAssertions: () => expect(nock.pendingMocks()).toEqual([]),
+	});
+});

packages/nodes-base/nodes/Microsoft/Outlook/test/v2/node/servicePrincipal/sendPerItemContinueOnFail.workflow.json

@@ -0,0 +1,105 @@
+{
+	"name": "Microsoft Outlook Service Principal Message Send Per Item ContinueOnFail",
+	"nodes": [
+		{
+			"parameters": {},
+			"id": "e524f588-b6a3-4849-8777-b32a8a755af5",
+			"name": "When clicking \"Execute Workflow\"",
+			"type": "n8n-nodes-base.manualTrigger",
+			"typeVersion": 1,
+			"position": [820, 360]
+		},
+		{
+			"parameters": {
+				"data": [
+					{ "mailbox": "contoso.com" },
+					{ "mailbox": "[email protected]" },
+					{ "mailbox": "[email protected]" }
+				]
+			},
+			"id": "e524f588-b6a3-4849-8777-b32a8a755af6",
+			"name": "Test Data",
+			"type": "n8n-nodes-testing.testData",
+			"typeVersion": 1,
+			"position": [930, 360]
+		},
+		{
+			"parameters": {
+				"authentication": "microsoftEntraServicePrincipalApi",
+				"mailbox": {
+					"__rl": true,
+					"mode": "id",
+					"value": "={{ $json.mailbox }}"
+				},
+				"resource": "message",
+				"operation": "send",
+				"toRecipients": "[email protected]",
+				"subject": "Hello",
+				"bodyContent": "message description",
+				"additionalFields": {
+					"bodyContentType": "Text"
+				}
+			},
+			"id": "baff6798-0304-4255-bdb0-dd3f2659373e",
+			"name": "Microsoft Outlook",
+			"type": "n8n-nodes-base.microsoftOutlook",
+			"typeVersion": 2,
+			"position": [1040, 360],
+			"onError": "continueRegularOutput",
+			"credentials": {
+				"microsoftEntraServicePrincipalApi": {
+					"id": "spCredId1",
+					"name": "Microsoft Entra Service Principal Test"
+				}
+			}
+		}
+	],
+	"pinData": {
+		"Microsoft Outlook": [
+			{
+				"json": {
+					"error": "The mailbox is not valid"
+				}
+			},
+			{
+				"json": {
+					"success": true
+				}
+			},
+			{
+				"json": {
+					"success": true
+				}
+			}
+		]
+	},
+	"connections": {
+		"When clicking \"Execute Workflow\"": {
+			"main": [
+				[
+					{
+						"node": "Test Data",
+						"type": "main",
+						"index": 0
+					}
+				]
+			]
+		},
+		"Test Data": {
+			"main": [
+				[
+					{
+						"node": "Microsoft Outlook",
+						"type": "main",
+						"index": 0
+					}
+				]
+			]
+		}
+	},
+	"active": false,
+	"settings": {
+		"executionOrder": "v1"
+	},
+	"tags": []
+}

packages/nodes-base/nodes/Microsoft/Outlook/test/v2/transport/index.test.ts

@@ -1,9 +1,11 @@
 import type { IDataObject, IExecuteFunctions, ILoadOptionsFunctions, INode } from 'n8n-workflow';
-import { NodeOperationError } from 'n8n-workflow';
+import { NodeApiError, NodeOperationError } from 'n8n-workflow';
 import type { Mock, Mocked } from 'vitest';
 import { mockDeep } from 'vitest-mock-extended';
 
 import {
+	downloadAttachments,
+	getMimeContent,
 	getOutlookCredentialType,
 	getSubfolders,
 	microsoftApiRequest,
@@ -43,7 +45,7 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 				graphApiBaseUrl: 'https://graph.microsoft.us',
 			});
 
-			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages');
+			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0);
 
 			expect(mockRequestWithAuthentication).toHaveBeenCalledWith(
 				'microsoftOutlookOAuth2Api',
@@ -62,7 +64,7 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 				graphApiBaseUrl: '',
 			});
 
-			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages');
+			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0);
 
 			expect(mockRequestWithAuthentication).toHaveBeenCalledWith(
 				'microsoftOutlookOAuth2Api',
@@ -78,7 +80,7 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 				oauthTokenData: { access_token: 'test-access-token' },
 			});
 
-			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages');
+			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0);
 
 			expect(mockRequestWithAuthentication).toHaveBeenCalledWith(
 				'microsoftOutlookOAuth2Api',
@@ -94,7 +96,7 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 				graphApiBaseUrl: 'https://graph.microsoft.com/',
 			});
 
-			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages');
+			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0);
 
 			expect(mockRequestWithAuthentication).toHaveBeenCalledWith(
 				'microsoftOutlookOAuth2Api',
@@ -110,7 +112,7 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 				graphApiBaseUrl: 'https://graph.microsoft.com///',
 			});
 
-			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages');
+			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0);
 
 			expect(mockRequestWithAuthentication).toHaveBeenCalledWith(
 				'microsoftOutlookOAuth2Api',
@@ -126,7 +128,7 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 				graphApiBaseUrl: 'https://graph.microsoft.us',
 			});
 
-			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages');
+			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0);
 
 			expect(mockRequestWithAuthentication).toHaveBeenCalledWith(
 				'microsoftOutlookOAuth2Api',
@@ -142,7 +144,7 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 				graphApiBaseUrl: 'https://dod-graph.microsoft.us',
 			});
 
-			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages');
+			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0);
 
 			expect(mockRequestWithAuthentication).toHaveBeenCalledWith(
 				'microsoftOutlookOAuth2Api',
@@ -158,7 +160,7 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 				graphApiBaseUrl: 'https://microsoftgraph.chinacloudapi.cn',
 			});
 
-			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages');
+			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0);
 
 			expect(mockRequestWithAuthentication).toHaveBeenCalledWith(
 				'microsoftOutlookOAuth2Api',
@@ -175,7 +177,7 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 			mockExecuteFunctions.getNodeParameter.mockReturnValue(undefined);
 			mockExecuteFunctions.getCredentials.mockResolvedValue({});
 
-			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages');
+			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0);
 
 			expect(mockExecuteFunctions.getCredentials).toHaveBeenCalledWith('microsoftOutlookOAuth2Api');
 			expect(mockRequestWithAuthentication).toHaveBeenCalledWith(
@@ -189,7 +191,7 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 			mockExecuteFunctions.getNodeParameter.mockReturnValue('microsoftOAuth2Api');
 			mockExecuteFunctions.getCredentials.mockResolvedValue({});
 
-			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages');
+			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0);
 
 			expect(mockExecuteFunctions.getCredentials).toHaveBeenCalledWith('microsoftOAuth2Api');
 			expect(mockRequestWithAuthentication).toHaveBeenCalledWith(
@@ -213,7 +215,7 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 				userPrincipalName: '[email protected]',
 			});
 
-			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages');
+			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0);
 
 			expect(mockRequestWithAuthentication).toHaveBeenCalledWith(
 				'microsoftOutlookOAuth2Api',
@@ -252,7 +254,7 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 		it('should target /users/{encoded-mailbox} and resolve the SP credential', async () => {
 			setupSP({ mailbox: '[email protected]' });
 
-			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages');
+			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0);
 
 			expect(mockExecuteFunctions.getCredentials).toHaveBeenCalledWith(
 				'microsoftEntraServicePrincipalApi',
@@ -272,7 +274,7 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 			// this covers the isResourceLocatorValue(raw) ? raw.value branch directly.
 			setupSP({ mailbox: { __rl: true, mode: 'id', value: '[email protected]' } });
 
-			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages');
+			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0);
 
 			expect(mockRequestWithAuthentication).toHaveBeenCalledWith(
 				'microsoftEntraServicePrincipalApi',
@@ -285,7 +287,7 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 		it('should pass a GUID mailbox through verbatim (nothing to percent-encode)', async () => {
 			setupSP({ mailbox: '11111111-1111-1111-1111-111111111111' });
 
-			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages');
+			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0);
 
 			expect(mockRequestWithAuthentication).toHaveBeenCalledWith(
 				'microsoftEntraServicePrincipalApi',
@@ -298,7 +300,7 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 		it('should carry a B2B guest (#EXT#) mailbox end-to-end into an encoded /users/{id} uri', async () => {
 			setupSP({ mailbox: 'user_contoso.com#EXT#@tenant.onmicrosoft.com' });
 
-			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages');
+			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0);
 
 			expect(mockRequestWithAuthentication).toHaveBeenCalledWith(
 				'microsoftEntraServicePrincipalApi',
@@ -311,7 +313,7 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 		it('should carry a "^"/"!" mailbox end-to-end into an encoded /users/{id} uri', async () => {
 			setupSP({ mailbox: 'joe^[email protected]' });
 
-			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages');
+			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0);
 
 			expect(mockRequestWithAuthentication).toHaveBeenCalledWith(
 				'microsoftEntraServicePrincipalApi',
@@ -324,7 +326,7 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 		it('should target the sovereign cloud base for the SP mailbox', async () => {
 			setupSP({ mailbox: '[email protected]', graphApiBaseUrl: 'https://graph.microsoft.us' });
 
-			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages');
+			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0);
 
 			expect(mockRequestWithAuthentication).toHaveBeenCalledWith(
 				'microsoftEntraServicePrincipalApi',
@@ -339,7 +341,7 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 			const nextLink =
 				'https://graph.microsoft.com/v1.0/users/user%40example.com/messages?$skip=10&$top=10';
 
-			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', {}, {}, nextLink);
+			await microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0, {}, {}, nextLink);
 
 			const callArgs = mockRequestWithAuthentication.mock.calls[0][1] as IDataObject;
 			expect(callArgs.uri).toBe(nextLink);
@@ -351,10 +353,10 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 			setupSP({ mailbox: '' });
 
 			await expect(
-				microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages'),
+				microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0),
 			).rejects.toThrow(NodeOperationError);
 			await expect(
-				microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages'),
+				microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0),
 			).rejects.toThrow('A mailbox is required for the Service Principal');
 			expect(mockRequestWithAuthentication).not.toHaveBeenCalled();
 		});
@@ -364,7 +366,7 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 			setupSP({ mailbox: '   ' });
 
 			await expect(
-				microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages'),
+				microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0),
 			).rejects.toThrow('A mailbox is required for the Service Principal');
 			expect(mockRequestWithAuthentication).not.toHaveBeenCalled();
 		});
@@ -375,10 +377,140 @@ describe('MicrosoftOutlookV2 - microsoftApiRequest', () => {
 			setupSP({ mailbox: 'contoso.com' });
 
 			await expect(
-				microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages'),
+				microsoftApiRequest.call(mockExecuteFunctions, 'GET', '/messages', 0),
 			).rejects.toThrow('The mailbox is not valid');
 			expect(mockRequestWithAuthentication).not.toHaveBeenCalled();
 		});
+
+		// The mailbox RLC accepts expressions, so execute call sites pass the loop index
+		// and the transport must read the mailbox at exactly that index. Reuses setupSP
+		// and only swaps in an index-aware mailbox read.
+		const setupSPPerItem = () => {
+			setupSP();
+			mockExecuteFunctions.getNodeParameter.mockImplementation(
+				(name: string, itemIndex?: number) => {
+					if (name === 'authentication') return 'microsoftEntraServicePrincipalApi';
+					if (name === 'mailbox')
+						return itemIndex === 1 ? '[email protected]' : '[email protected]';
+					return undefined;
+				},
+			);
+		};
+
+		it('should resolve the mailbox at the passed itemIndex', async () => {
+			setupSPPerItem();
+
+			await microsoftApiRequest.call(
+				mockExecuteFunctions,
+				'GET',
+				'/messages',
+				0,
+				{},
+				{},
+				undefined,
+				{},
+				{ json: true },
+			);
+			await microsoftApiRequest.call(
+				mockExecuteFunctions,
+				'GET',
+				'/messages',
+				1,
+				{},
+				{},
+				undefined,
+				{},
+				{ json: true },
+			);
+
+			expect(mockRequestWithAuthentication).toHaveBeenNthCalledWith(
+				1,
+				'microsoftEntraServicePrincipalApi',
+				expect.objectContaining({
+					uri: 'https://graph.microsoft.com/v1.0/users/user1%40example.com/messages',
+				}),
+			);
+			expect(mockRequestWithAuthentication).toHaveBeenNthCalledWith(
+				2,
+				'microsoftEntraServicePrincipalApi',
+				expect.objectContaining({
+					uri: 'https://graph.microsoft.com/v1.0/users/user2%40example.com/messages',
+				}),
+			);
+		});
+
+		it('should attribute a Graph error to the passed itemIndex (prepareApiError path)', async () => {
+			setupSP();
+			// "bad request" message + parseable description route the error through
+			// prepareApiError, which must receive the forwarded index.
+			mockRequestWithAuthentication.mockRejectedValue(
+				Object.assign(new Error('bad request'), {
+					description: '400 - {"error":{"code":"ErrorInvalidRequest","message":"broken"}} - broken',
+				}),
+			);
+
+			let caught: unknown;
+			try {
+				await microsoftApiRequest.call(
+					mockExecuteFunctions,
+					'GET',
+					'/messages',
+					2,
+					{},
+					{},
+					undefined,
+					{},
+					{ json: true },
+				);
+			} catch (error) {
+				caught = error;
+			}
+
+			expect(caught).toBeInstanceOf(NodeApiError);
+			expect((caught as NodeApiError).context.itemIndex).toBe(2);
+		});
+
+		it('should download attachments from the mailbox at the passed itemIndex', async () => {
+			setupSPPerItem();
+			mockRequestWithAuthentication
+				.mockResolvedValueOnce({
+					value: [{ id: 'att1', name: 'file.txt', contentType: 'text/plain' }],
+				})
+				.mockResolvedValueOnce({ body: 'DATA', headers: {} });
+
+			await downloadAttachments.call(
+				mockExecuteFunctions,
+				{ id: 'MSG1', hasAttachments: true },
+				'attachment_',
+				1,
+			);
+
+			const uris = mockRequestWithAuthentication.mock.calls.map(
+				(call) => (call[1] as IDataObject).uri,
+			);
+			expect(uris).toEqual([
+				'https://graph.microsoft.com/v1.0/users/user2%40example.com/messages/MSG1/attachments',
+				'https://graph.microsoft.com/v1.0/users/user2%40example.com/messages/MSG1/attachments/att1/$value',
+			]);
+		});
+
+		it('should fetch MIME content from the mailbox at the passed itemIndex', async () => {
+			setupSPPerItem();
+			mockRequestWithAuthentication.mockResolvedValue({
+				body: 'MIME',
+				// eslint-disable-next-line @typescript-eslint/naming-convention
+				headers: { 'content-type': 'message/rfc822' },
+			});
+
+			await getMimeContent.call(mockExecuteFunctions, 'MSG1', 'data', 1);
+
+			expect(mockRequestWithAuthentication).toHaveBeenCalledWith(
+				'microsoftEntraServicePrincipalApi',
+				expect.objectContaining({
+					uri: 'https://graph.microsoft.com/v1.0/users/user2%40example.com/messages/MSG1/$value',
+				}),
+			);
+		});
 	});
 });
 
@@ -401,7 +533,7 @@ describe('MicrosoftOutlookV2 - getSubfolders', () => {
 			{ id: 'folder2', displayName: 'Sent Items', childFolderCount: 0 },
 		];
 
-		const result = await getSubfolders.call(mockLoadOptionsFunctions, folders);
+		const result = await getSubfolders.call(mockLoadOptionsFunctions, folders, 0);
 
 		expect(
 			mockLoadOptionsFunctions.helpers.requestWithAuthentication as Mock,
@@ -422,7 +554,7 @@ describe('MicrosoftOutlookV2 - getSubfolders', () => {
 				value: [{ id: 'sub2', displayName: 'Projects', childFolderCount: 0 }],
 			});
 
-		const result = await getSubfolders.call(mockLoadOptionsFunctions, folders);
+		const result = await getSubfolders.call(mockLoadOptionsFunctions, folders, 0);
 
 		expect(
 			mockLoadOptionsFunctions.helpers.requestWithAuthentication as Mock,
@@ -445,7 +577,7 @@ describe('MicrosoftOutlookV2 - getSubfolders', () => {
 				value: [{ id: 'q2', displayName: 'Q2', childFolderCount: 0 }],
 			});
 
-		const result = await getSubfolders.call(mockLoadOptionsFunctions, folders, true);
+		const result = await getSubfolders.call(mockLoadOptionsFunctions, folders, 0, true);
 
 		expect(result).toEqual([
 			{ id: 'inbox', displayName: 'Inbox', childFolderCount: 1 },
@@ -461,7 +593,7 @@ describe('MicrosoftOutlookV2 - getSubfolders', () => {
 			value: [{ id: 'work', displayName: 'Work', childFolderCount: 0 }],
 		});
 
-		const result = await getSubfolders.call(mockLoadOptionsFunctions, folders);
+		const result = await getSubfolders.call(mockLoadOptionsFunctions, folders, 0);
 
 		expect(result).toEqual([
 			{ id: 'inbox', displayName: 'Inbox', childFolderCount: 1 },

packages/nodes-base/nodes/Microsoft/Outlook/trigger/GenericFunctions.ts

@@ -57,7 +57,8 @@ export async function getPollResponse(
 			const results = await Promise.all(
 				endpoints.map(
 					async (endpoint) =>
-						await microsoftApiRequestAllItems.call(this, 'value', 'GET', endpoint, undefined, {
+						// Poll context: 0 is the transport's fallback read, not an item index.
+						await microsoftApiRequestAllItems.call(this, 'value', 'GET', endpoint, 0, undefined, {
 							...qs,
 						}),
 				),
@@ -71,7 +72,8 @@ export async function getPollResponse(
 			const results = await Promise.all(
 				endpoints.map(
 					async (endpoint) =>
-						await microsoftApiRequest.call(this, 'GET', endpoint, undefined, { ...qs }),
+						// Poll context: 0 is the transport's fallback read, not an item index.
+						await microsoftApiRequest.call(this, 'GET', endpoint, 0, undefined, { ...qs }),
 				),
 			);
 			responseData = results.flatMap((result) => (result.value as IDataObject[]) ?? []).slice(0, 1);
@@ -85,7 +87,13 @@ export async function getPollResponse(
 
 		if (options.downloadAttachments) {
 			const prefix = (options.attachmentsPrefix as string) || 'attachment_';
-			executionData = await downloadAttachments.call(this, responseData as IDataObject[], prefix);
+			// Poll context: 0 is the transport's fallback read, not an item index.
+			executionData = await downloadAttachments.call(
+				this,
+				responseData as IDataObject[],
+				prefix,
+				0,
+			);
 		} else {
 			executionData = this.helpers.returnJsonArray(responseData as IDataObject[]);
 		}

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/calendar/create.operation.ts

@@ -107,7 +107,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 		...additionalFields,
 	};
 
-	const responseData = await microsoftApiRequest.call(this, 'POST', endpoint, body);
+	const responseData = await microsoftApiRequest.call(this, 'POST', endpoint, index, body);
 
 	const executionData = this.helpers.constructExecutionMetaData(
 		this.helpers.returnJsonArray(responseData as IDataObject),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/calendar/delete.operation.ts

@@ -21,7 +21,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 		extractValue: true,
 	}) as string;
 
-	await microsoftApiRequest.call(this, 'DELETE', `/calendars/${calendarId}`);
+	await microsoftApiRequest.call(this, 'DELETE', `/calendars/${calendarId}`, index);
 
 	const executionData = this.helpers.constructExecutionMetaData(
 		this.helpers.returnJsonArray({ success: true }),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/calendar/get.operation.ts

@@ -27,6 +27,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 		this,
 		'GET',
 		`/calendars/${calendarId}`,
+		index,
 		undefined,
 		qs,
 	);

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/calendar/getAll.operation.ts

@@ -62,12 +62,13 @@ export async function execute(this: IExecuteFunctions, index: number) {
 			'value',
 			'GET',
 			endpoint,
+			index,
 			undefined,
 			qs,
 		);
 	} else {
 		qs.$top = this.getNodeParameter('limit', index);
-		responseData = await microsoftApiRequest.call(this, 'GET', endpoint, undefined, qs);
+		responseData = await microsoftApiRequest.call(this, 'GET', endpoint, index, undefined, qs);
 		responseData = responseData.value;
 	}
 

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/calendar/update.operation.ts

@@ -99,7 +99,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 		...updateFields,
 	};
 
-	const responseData = await microsoftApiRequest.call(this, 'PATCH', endpoint, body);
+	const responseData = await microsoftApiRequest.call(this, 'PATCH', endpoint, index, body);
 
 	const executionData = this.helpers.constructExecutionMetaData(
 		this.helpers.returnJsonArray(responseData as IDataObject),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/contact/create.operation.ts

@@ -53,7 +53,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 		body.surname = surname;
 	}
 
-	const responseData = await microsoftApiRequest.call(this, 'POST', '/contacts', body);
+	const responseData = await microsoftApiRequest.call(this, 'POST', '/contacts', index, body);
 
 	const executionData = this.helpers.constructExecutionMetaData(
 		this.helpers.returnJsonArray(responseData as IDataObject),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/contact/delete.operation.ts

@@ -20,7 +20,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 	const contactId = this.getNodeParameter('contactId', index, undefined, {
 		extractValue: true,
 	}) as string;
-	await microsoftApiRequest.call(this, 'DELETE', `/contacts/${contactId}`);
+	await microsoftApiRequest.call(this, 'DELETE', `/contacts/${contactId}`, index);
 
 	const executionData = this.helpers.constructExecutionMetaData(
 		this.helpers.returnJsonArray({ success: true }),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/contact/get.operation.ts

@@ -74,6 +74,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 		this,
 		'GET',
 		`/contacts/${contactId}`,
+		index,
 		undefined,
 		qs,
 	);

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/contact/getAll.operation.ts

@@ -121,12 +121,13 @@ export async function execute(this: IExecuteFunctions, index: number) {
 			'value',
 			'GET',
 			endpoint,
+			index,
 			undefined,
 			qs,
 		);
 	} else {
 		qs.$top = this.getNodeParameter('limit', index);
-		responseData = await microsoftApiRequest.call(this, 'GET', endpoint, undefined, qs);
+		responseData = await microsoftApiRequest.call(this, 'GET', endpoint, index, undefined, qs);
 		responseData = responseData.value;
 	}
 

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/contact/update.operation.ts

@@ -39,6 +39,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 		this,
 		'PATCH',
 		`/contacts/${contactId}`,
+		index,
 		body,
 	);
 

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/draft/create.operation.ts

@@ -244,7 +244,7 @@ export async function execute(this: IExecuteFunctions, index: number, _: INodeEx
 		);
 	}
 
-	const responseData = await microsoftApiRequest.call(this, 'POST', '/messages', body, {});
+	const responseData = await microsoftApiRequest.call(this, 'POST', '/messages', index, body, {});
 
 	const executionData = this.helpers.constructExecutionMetaData(
 		this.helpers.returnJsonArray(responseData as IDataObject),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/draft/delete.operation.ts

@@ -20,7 +20,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 	const draftId = this.getNodeParameter('draftId', index, undefined, {
 		extractValue: true,
 	}) as string;
-	await microsoftApiRequest.call(this, 'DELETE', `/messages/${draftId}`);
+	await microsoftApiRequest.call(this, 'DELETE', `/messages/${draftId}`, index);
 
 	const executionData = this.helpers.constructExecutionMetaData(
 		this.helpers.returnJsonArray({ success: true }),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/draft/get.operation.ts

@@ -107,7 +107,14 @@ export async function execute(this: IExecuteFunctions, index: number) {
 			'id,conversationId,subject,bodyPreview,from,toRecipients,categories,hasAttachments';
 	}
 
-	responseData = await microsoftApiRequest.call(this, 'GET', `/messages/${draftId}`, undefined, qs);
+	responseData = await microsoftApiRequest.call(
+		this,
+		'GET',
+		`/messages/${draftId}`,
+		index,
+		undefined,
+		qs,
+	);
 
 	if (output === 'simple') {
 		responseData = simplifyOutputMessages([responseData as IDataObject]);
@@ -117,7 +124,12 @@ export async function execute(this: IExecuteFunctions, index: number) {
 
 	if (options.downloadAttachments) {
 		const prefix = (options.attachmentsPrefix as string) || 'attachment_';
-		executionData = await downloadAttachments.call(this, responseData as IDataObject, prefix);
+		executionData = await downloadAttachments.call(
+			this,
+			responseData as IDataObject,
+			prefix,
+			index,
+		);
 	} else {
 		executionData = this.helpers.constructExecutionMetaData(
 			this.helpers.returnJsonArray(responseData as IDataObject),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/draft/send.operation.ts

@@ -37,13 +37,13 @@ export async function execute(this: IExecuteFunctions, index: number) {
 			.filter((email) => email);
 
 		if (recipients.length !== 0) {
-			await microsoftApiRequest.call(this, 'PATCH', `/messages/${draftId}`, {
+			await microsoftApiRequest.call(this, 'PATCH', `/messages/${draftId}`, index, {
 				toRecipients: recipients.map((recipient: string) => makeRecipient(recipient)),
 			});
 		}
 	}
 
-	await microsoftApiRequest.call(this, 'POST', `/messages/${draftId}/send`);
+	await microsoftApiRequest.call(this, 'POST', `/messages/${draftId}/send`, index);
 
 	const executionData = this.helpers.constructExecutionMetaData(
 		this.helpers.returnJsonArray({ success: true }),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/draft/update.operation.ts

@@ -195,6 +195,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 		this,
 		'PATCH',
 		`/messages/${draftId}`,
+		index,
 		body,
 		{},
 	);

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/event/create.operation.ts

@@ -286,7 +286,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 		...additionalFields,
 	};
 
-	const responseData = await microsoftApiRequest.call(this, 'POST', endpoint, body);
+	const responseData = await microsoftApiRequest.call(this, 'POST', endpoint, index, body);
 
 	const executionData = this.helpers.constructExecutionMetaData(
 		this.helpers.returnJsonArray(responseData as IDataObject),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/event/delete.operation.ts

@@ -24,7 +24,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 		}) as string,
 	);
 
-	await microsoftApiRequest.call(this, 'DELETE', `/calendar/events/${eventId}`);
+	await microsoftApiRequest.call(this, 'DELETE', `/calendar/events/${eventId}`, index);
 
 	const executionData = this.helpers.constructExecutionMetaData(
 		this.helpers.returnJsonArray({ success: true }),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/event/get.operation.ts

@@ -75,7 +75,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 
 	const endpoint = `/calendar/events/${eventId}`;
 
-	const responseData = await microsoftApiRequest.call(this, 'GET', endpoint, undefined, qs);
+	const responseData = await microsoftApiRequest.call(this, 'GET', endpoint, index, undefined, qs);
 
 	const executionData = this.helpers.constructExecutionMetaData(
 		this.helpers.returnJsonArray(responseData as IDataObject[]),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/event/getAll.operation.ts

@@ -166,7 +166,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 	const fromAllCalendars = this.getNodeParameter('fromAllCalendars', index) as boolean;
 
 	if (fromAllCalendars) {
-		const response = await microsoftApiRequest.call(this, 'GET', '/calendars', undefined, {
+		const response = await microsoftApiRequest.call(this, 'GET', '/calendars', index, undefined, {
 			$select: 'id',
 		});
 		for (const calendar of response.value) {
@@ -192,6 +192,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 				'value',
 				'GET',
 				endpoint,
+				index,
 				undefined,
 				qs,
 			);
@@ -201,7 +202,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 
 			if (qs.$top <= 0) break;
 
-			const response = await microsoftApiRequest.call(this, 'GET', endpoint, undefined, qs);
+			const response = await microsoftApiRequest.call(this, 'GET', endpoint, index, undefined, qs);
 			responseData.push(...response.value);
 		}
 	}

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/event/update.operation.ts

@@ -280,7 +280,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 
 	const endpoint = `/calendar/events/${eventId}`;
 
-	const responseData = await microsoftApiRequest.call(this, 'PATCH', endpoint, body);
+	const responseData = await microsoftApiRequest.call(this, 'PATCH', endpoint, index, body);
 
 	const executionData = this.helpers.constructExecutionMetaData(
 		this.helpers.returnJsonArray(responseData as IDataObject),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/folder/create.operation.ts

@@ -56,7 +56,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 		endpoint = '/mailFolders';
 	}
 
-	const responseData = await microsoftApiRequest.call(this, 'POST', endpoint, body);
+	const responseData = await microsoftApiRequest.call(this, 'POST', endpoint, index, body);
 
 	const executionData = this.helpers.constructExecutionMetaData(
 		this.helpers.returnJsonArray(responseData as IDataObject[]),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/folder/delete.operation.ts

@@ -24,7 +24,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 		}) as string,
 	);
 
-	await microsoftApiRequest.call(this, 'DELETE', `/mailFolders/${folderId}`);
+	await microsoftApiRequest.call(this, 'DELETE', `/mailFolders/${folderId}`, index);
 
 	const executionData = this.helpers.constructExecutionMetaData(
 		this.helpers.returnJsonArray({ success: true }),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/folder/get.operation.ts

@@ -58,6 +58,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 		this,
 		'GET',
 		`/mailFolders/${folderId}`,
+		index,
 		{},
 		qs,
 	);

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/folder/getAll.operation.ts

@@ -93,15 +93,23 @@ export async function execute(this: IExecuteFunctions, index: number) {
 	}
 
 	if (returnAll) {
-		responseData = await microsoftApiRequestAllItems.call(this, 'value', 'GET', endpoint, {}, qs);
+		responseData = await microsoftApiRequestAllItems.call(
+			this,
+			'value',
+			'GET',
+			endpoint,
+			index,
+			{},
+			qs,
+		);
 	} else {
 		qs.$top = this.getNodeParameter('limit', index);
-		responseData = await microsoftApiRequest.call(this, 'GET', endpoint, {}, qs);
+		responseData = await microsoftApiRequest.call(this, 'GET', endpoint, index, {}, qs);
 		responseData = responseData.value;
 	}
 
 	if (options.includeChildFolders) {
-		responseData = await getSubfolders.call(this, responseData as IDataObject[]);
+		responseData = await getSubfolders.call(this, responseData as IDataObject[], index);
 	}
 
 	const executionData = this.helpers.constructExecutionMetaData(

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/folder/update.operation.ts

@@ -35,9 +35,13 @@ export async function execute(this: IExecuteFunctions, index: number) {
 	);
 	const displayName = this.getNodeParameter('displayName', index, undefined) as string;
 
-	const responseData = await microsoftApiRequest.call(this, 'PATCH', `/mailFolders/${folderId}`, {
-		displayName,
-	});
+	const responseData = await microsoftApiRequest.call(
+		this,
+		'PATCH',
+		`/mailFolders/${folderId}`,
+		index,
+		{ displayName },
+	);
 
 	const executionData = this.helpers.constructExecutionMetaData(
 		this.helpers.returnJsonArray(responseData as IDataObject),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/folderMessage/getAll.operation.ts

@@ -274,12 +274,13 @@ export async function execute(this: IExecuteFunctions, index: number) {
 			'value',
 			'GET',
 			endpoint,
+			index,
 			undefined,
 			qs,
 		);
 	} else {
 		qs.$top = this.getNodeParameter('limit', index);
-		responseData = await microsoftApiRequest.call(this, 'GET', endpoint, undefined, qs);
+		responseData = await microsoftApiRequest.call(this, 'GET', endpoint, index, undefined, qs);
 		responseData = responseData.value;
 	}
 
@@ -291,7 +292,12 @@ export async function execute(this: IExecuteFunctions, index: number) {
 
 	if (options.downloadAttachments) {
 		const prefix = (options.attachmentsPrefix as string) || 'attachment_';
-		executionData = await downloadAttachments.call(this, responseData as IDataObject, prefix);
+		executionData = await downloadAttachments.call(
+			this,
+			responseData as IDataObject,
+			prefix,
+			index,
+		);
 	} else {
 		executionData = this.helpers.constructExecutionMetaData(
 			this.helpers.returnJsonArray(responseData as IDataObject[]),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/message/delete.operation.ts

@@ -20,7 +20,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 	const messageId = this.getNodeParameter('messageId', index, undefined, {
 		extractValue: true,
 	}) as string;
-	await microsoftApiRequest.call(this, 'DELETE', `/messages/${messageId}`);
+	await microsoftApiRequest.call(this, 'DELETE', `/messages/${messageId}`, index);
 
 	const executionData = this.helpers.constructExecutionMetaData(
 		this.helpers.returnJsonArray({ success: true }),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/message/get.operation.ts

@@ -142,6 +142,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 		this,
 		'GET',
 		`/messages/${messageId}`,
+		index,
 		undefined,
 		qs,
 	);
@@ -154,7 +155,12 @@ export async function execute(this: IExecuteFunctions, index: number) {
 
 	if (options.downloadAttachments) {
 		const prefix = (options.attachmentsPrefix as string) || 'attachment_';
-		executionData = await downloadAttachments.call(this, responseData as IDataObject, prefix);
+		executionData = await downloadAttachments.call(
+			this,
+			responseData as IDataObject,
+			prefix,
+			index,
+		);
 	} else {
 		executionData = this.helpers.constructExecutionMetaData(
 			this.helpers.returnJsonArray(responseData as IDataObject),
@@ -170,6 +176,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 			this,
 			messageId,
 			binaryPropertyName as string,
+			index,
 			outputFileName as string,
 		);
 

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/message/getAll.operation.ts

@@ -284,12 +284,13 @@ export async function execute(this: IExecuteFunctions, index: number) {
 			'value',
 			'GET',
 			endpoint,
+			index,
 			undefined,
 			qs,
 		);
 	} else {
 		qs.$top = this.getNodeParameter('limit', index);
-		responseData = await microsoftApiRequest.call(this, 'GET', endpoint, undefined, qs);
+		responseData = await microsoftApiRequest.call(this, 'GET', endpoint, index, undefined, qs);
 		responseData = responseData.value;
 	}
 
@@ -301,7 +302,12 @@ export async function execute(this: IExecuteFunctions, index: number) {
 
 	if (options.downloadAttachments) {
 		const prefix = (options.attachmentsPrefix as string) || 'attachment_';
-		executionData = await downloadAttachments.call(this, responseData as IDataObject, prefix);
+		executionData = await downloadAttachments.call(
+			this,
+			responseData as IDataObject,
+			prefix,
+			index,
+		);
 	} else {
 		executionData = this.helpers.constructExecutionMetaData(
 			this.helpers.returnJsonArray(responseData as IDataObject[]),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/message/move.operation.ts

@@ -32,7 +32,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 		destinationId,
 	};
 
-	await microsoftApiRequest.call(this, 'POST', `/messages/${messageId}/move`, body);
+	await microsoftApiRequest.call(this, 'POST', `/messages/${messageId}/move`, index, body);
 
 	const executionData = this.helpers.constructExecutionMetaData(
 		this.helpers.returnJsonArray({ success: true }),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/message/reply.operation.ts

@@ -248,6 +248,7 @@ export async function execute(this: IExecuteFunctions, index: number, _: INodeEx
 		this,
 		'POST',
 		`/messages/${messageId}/${action}`,
+		index,
 		body,
 	);
 
@@ -283,6 +284,7 @@ export async function execute(this: IExecuteFunctions, index: number, _: INodeEx
 				this,
 				'POST',
 				`/messages/${responseData.id}/attachments`,
+				index,
 				attachment,
 				{},
 			);
@@ -290,7 +292,7 @@ export async function execute(this: IExecuteFunctions, index: number, _: INodeEx
 	}
 
 	if (!saveAsDraft) {
-		await microsoftApiRequest.call(this, 'POST', `/messages/${responseData.id}/send`);
+		await microsoftApiRequest.call(this, 'POST', `/messages/${responseData.id}/send`, index);
 	}
 
 	const executionData = this.helpers.constructExecutionMetaData(

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/message/send.operation.ts

@@ -258,7 +258,7 @@ export async function execute(this: IExecuteFunctions, index: number, _: INodeEx
 		saveToSentItems,
 	};
 
-	await microsoftApiRequest.call(this, 'POST', '/sendMail', body, {});
+	await microsoftApiRequest.call(this, 'POST', '/sendMail', index, body, {});
 
 	const executionData = this.helpers.constructExecutionMetaData(
 		this.helpers.returnJsonArray({ success: true }),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/message/sendAndWait.operation.ts

@@ -56,7 +56,7 @@ export async function execute(this: IExecuteFunctions, index: number, items: INo
 
 	const body: IDataObject = { message };
 
-	await microsoftApiRequest.call(this, 'POST', '/sendMail', body);
+	await microsoftApiRequest.call(this, 'POST', '/sendMail', index, body);
 
 	return items;
 }

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/message/update.operation.ts

@@ -194,6 +194,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 			this,
 			'POST',
 			`/messages/${messageId}/move`,
+			index,
 			body,
 		);
 
@@ -215,7 +216,14 @@ export async function execute(this: IExecuteFunctions, index: number) {
 		throw new NodeOperationError(this.getNode(), 'No fields to update got specified');
 	}
 
-	responseData = await microsoftApiRequest.call(this, 'PATCH', `/messages/${messageId}`, body, {});
+	responseData = await microsoftApiRequest.call(
+		this,
+		'PATCH',
+		`/messages/${messageId}`,
+		index,
+		body,
+		{},
+	);
 
 	const executionData = this.helpers.constructExecutionMetaData(
 		this.helpers.returnJsonArray(responseData as IDataObject),

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/messageAttachment/add.operation.ts

@@ -91,6 +91,7 @@ export async function execute(this: IExecuteFunctions, index: number, _: INodeEx
 			this,
 			'POST',
 			`/messages/${messageId}/attachments/createUploadSession`,
+			index,
 			body,
 		);
 		const uploadUrl = responseData.uploadUrl;
@@ -129,6 +130,7 @@ export async function execute(this: IExecuteFunctions, index: number, _: INodeEx
 			this,
 			'POST',
 			`/messages/${messageId}/attachments`,
+			index,
 			body,
 			{},
 		);

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/messageAttachment/download.operation.ts

@@ -43,6 +43,7 @@ export async function execute(this: IExecuteFunctions, index: number, items: INo
 		this,
 		'GET',
 		`/messages/${messageId}/attachments/${attachmentId}`,
+		index,
 		undefined,
 		{ $select: 'id,name,contentType' },
 	);
@@ -57,6 +58,7 @@ export async function execute(this: IExecuteFunctions, index: number, items: INo
 		this,
 		'GET',
 		`/messages/${messageId}/attachments/${attachmentId}/$value`,
+		index,
 		undefined,
 		{},
 		undefined,

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/messageAttachment/get.operation.ts

@@ -83,6 +83,7 @@ export async function execute(this: IExecuteFunctions, index: number) {
 		this,
 		'GET',
 		`/messages/${messageId}/attachments/${attachmentId}`,
+		index,
 		undefined,
 		qs,
 	);

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/messageAttachment/getAll.operation.ts

@@ -84,12 +84,13 @@ export async function execute(this: IExecuteFunctions, index: number) {
 			'value',
 			'GET',
 			endpoint,
+			index,
 			undefined,
 			qs,
 		);
 	} else {
 		qs.$top = this.getNodeParameter('limit', index);
-		responseData = await microsoftApiRequest.call(this, 'GET', endpoint, undefined, qs);
+		responseData = await microsoftApiRequest.call(this, 'GET', endpoint, index, undefined, qs);
 		responseData = responseData.value;
 	}
 

packages/nodes-base/nodes/Microsoft/Outlook/v2/actions/router.ts

@@ -1,5 +1,5 @@
 import type { IExecuteFunctions, INodeExecutionData, JsonObject } from 'n8n-workflow';
-import { NodeApiError, NodeOperationError, SEND_AND_WAIT_OPERATION } from 'n8n-workflow';
+import { NodeOperationError, SEND_AND_WAIT_OPERATION } from 'n8n-workflow';
 
 import * as calendar from './calendar';
 import * as contact from './contact';
@@ -11,6 +11,7 @@ import * as message from './message';
 import * as messageAttachment from './messageAttachment';
 import type { MicrosoftOutlook } from './node.type';
 import { configureWaitTillDate } from '../../../../../utils/sendAndWait/configureWaitTillDate.util';
+import { stampItemIndexOnError } from '../../../GenericFunctions';
 
 export async function router(this: IExecuteFunctions) {
 	const items = this.getInputData();
@@ -90,14 +91,8 @@ export async function router(this: IExecuteFunctions) {
 				returnData.push(...executionErrorData);
 				continue;
 			}
-			//NodeApiError will be missing the itemIndex, add it
-			if (error instanceof NodeApiError && error?.context?.itemIndex === undefined) {
-				if (error.context === undefined) {
-					error.context = {};
-				}
-				error.context.itemIndex = i;
-			}
-			throw error;
+			// A NodeError from the transport may be missing the itemIndex, add it
+			throw stampItemIndexOnError(error, i);
 		}
 	}
 	return [returnData];

packages/nodes-base/nodes/Microsoft/Outlook/v2/descriptions/mailbox.description.ts

@@ -17,10 +17,10 @@ export const mailboxRLC: INodeProperties = {
 	type: 'resourceLocator',
 	default: { mode: 'id', value: '' },
 	required: true,
-	// Resolved once per run (from the first item) and reused for every item, so it accepts a fixed
-	// value or an expression; for per-item targeting, feed a single item or use Loop Over Items.
+	// Shared with the trigger: the action node evaluates this per input item; the
+	// trigger resolves it once per poll.
 	description:
-		'The mailbox the Service Principal should act on. Applies to the whole node (every item in the execution).',
+		'The mailbox the Service Principal should act on. In the action node this is evaluated per input item (an expression can target a different mailbox per item); the trigger resolves it once.',
 	modes: [
 		{
 			displayName: 'By ID',

packages/nodes-base/nodes/Microsoft/Outlook/v2/methods/listSearch.ts

@@ -3,6 +3,9 @@ import type { IDataObject, ILoadOptionsFunctions, INodeListSearchResult } from '
 import { encodeOutlookId } from '../helpers/utils';
 import { getSubfolders, microsoftApiRequest } from '../transport';
 
+// listSearch context throughout this file: the transport's trailing `0` is its
+// fallback read (getNodeParameter's 2nd arg here is a fallback, not an item index).
+
 async function search(
 	this: ILoadOptionsFunctions,
 	resource: string,
@@ -17,6 +20,7 @@ async function search(
 			this,
 			'GET',
 			'',
+			0,
 			undefined,
 			undefined,
 			paginationToken, // paginationToken contains the full URL
@@ -32,7 +36,7 @@ async function search(
 			qs.$filter = `contains(${nameProperty}, '${filterValue}')`;
 		}
 
-		response = await microsoftApiRequest.call(this, 'GET', resource, undefined, qs);
+		response = await microsoftApiRequest.call(this, 'GET', resource, 0, undefined, qs);
 	}
 
 	return {
@@ -74,6 +78,7 @@ export async function searchDrafts(
 			this,
 			'GET',
 			'',
+			0,
 			undefined,
 			undefined,
 			paginationToken, // paginationToken contains the full URL
@@ -90,7 +95,7 @@ export async function searchDrafts(
 			qs.$filter += ` AND contains(${'subject'}, '${filterValue}')`;
 		}
 
-		response = await microsoftApiRequest.call(this, 'GET', '/messages', undefined, qs);
+		response = await microsoftApiRequest.call(this, 'GET', '/messages', 0, undefined, qs);
 	}
 
 	return {
@@ -117,6 +122,7 @@ export async function searchMessages(
 			this,
 			'GET',
 			'',
+			0,
 			undefined,
 			undefined,
 			paginationToken, // paginationToken contains the full URL
@@ -132,7 +138,7 @@ export async function searchMessages(
 			qs.$filter = `contains(${'subject'}, '${filterValue}')`;
 		}
 
-		response = await microsoftApiRequest.call(this, 'GET', '/messages', undefined, qs);
+		response = await microsoftApiRequest.call(this, 'GET', '/messages', 0, undefined, qs);
 	}
 
 	return {
@@ -163,6 +169,7 @@ export async function searchEvents(
 			this,
 			'GET',
 			'',
+			0,
 			undefined,
 			undefined,
 			paginationToken, // paginationToken contains the full URL
@@ -182,6 +189,7 @@ export async function searchEvents(
 			this,
 			'GET',
 			`/calendars/${calendarId}/events`,
+			0,
 			undefined,
 			qs,
 		);
@@ -211,6 +219,7 @@ export async function searchFolders(
 			this,
 			'GET',
 			'',
+			0,
 			undefined,
 			undefined,
 			paginationToken, // paginationToken contains the full URL
@@ -220,10 +229,10 @@ export async function searchFolders(
 			$top: 100,
 		};
 
-		response = await microsoftApiRequest.call(this, 'GET', '/mailFolders', undefined, qs);
+		response = await microsoftApiRequest.call(this, 'GET', '/mailFolders', 0, undefined, qs);
 	}
 
-	let folders = await getSubfolders.call(this, response.value as IDataObject[], true);
+	let folders = await getSubfolders.call(this, response.value as IDataObject[], 0, true);
 
 	if (filter) {
 		filter = filter.toLowerCase();
@@ -259,6 +268,7 @@ export async function searchAttachments(
 			this,
 			'GET',
 			'',
+			0,
 			undefined,
 			undefined,
 			paginationToken, // paginationToken contains the full URL
@@ -273,6 +283,7 @@ export async function searchAttachments(
 			this,
 			'GET',
 			`/messages/${messageId}/attachments`,
+			0,
 			undefined,
 			qs,
 		);

packages/nodes-base/nodes/Microsoft/Outlook/v2/methods/loadOptions.ts

@@ -2,6 +2,9 @@ import type { ILoadOptionsFunctions, INodePropertyOptions } from 'n8n-workflow';
 
 import { getSubfolders, microsoftApiRequestAllItems } from '../transport';
 
+// loadOptions context throughout this file: the transport's trailing `0` is its
+// fallback read (getNodeParameter's 2nd arg here is a fallback, not an item index).
+
 export async function getCategoriesNames(
 	this: ILoadOptionsFunctions,
 ): Promise<INodePropertyOptions[]> {
@@ -11,6 +14,7 @@ export async function getCategoriesNames(
 		'value',
 		'GET',
 		'/outlook/masterCategories',
+		0,
 	);
 	for (const category of categories) {
 		returnData.push({
@@ -23,8 +27,15 @@ export async function getCategoriesNames(
 
 export async function getFolders(this: ILoadOptionsFunctions): Promise<INodePropertyOptions[]> {
 	const returnData: INodePropertyOptions[] = [];
-	const response = await microsoftApiRequestAllItems.call(this, 'value', 'GET', '/mailFolders', {});
-	const folders = await getSubfolders.call(this, response, true);
+	const response = await microsoftApiRequestAllItems.call(
+		this,
+		'value',
+		'GET',
+		'/mailFolders',
+		0,
+		{},
+	);
+	const folders = await getSubfolders.call(this, response, 0, true);
 	for (const folder of folders) {
 		returnData.push({
 			name: folder.displayName as string,
@@ -43,6 +54,7 @@ export async function getCalendarGroups(
 		'value',
 		'GET',
 		'/calendarGroups',
+		0,
 		{},
 	);
 	for (const calendar of calendars) {

packages/nodes-base/nodes/Microsoft/Outlook/v2/transport/index.ts

@@ -40,33 +40,40 @@ export function getOutlookCredentialType(
  * credential, app-only Graph has no `/me`, so the node's `mailbox` parameter is
  * read, validated, and returned as the bare (un-encoded) UPN/ID.
  *
- * The mailbox is read at the fixed item index 0 and treated as a per-node constant
- * for the whole run — the same contract as the `authentication` selector. Encoding
- * happens once at the URL-build site in `microsoftApiRequest`.
+ * The mailbox accepts expressions and is resolved per item: execute call sites pass
+ * the loop's item index; poll/loadOptions call sites pass a literal 0 — in those
+ * contexts `getNodeParameter`'s 2nd arg is a fallback, not an index. Encoding happens
+ * once at the URL-build site in `microsoftApiRequest`.
  */
 export function resolveMailbox(
 	this: IExecuteFunctions | IExecuteSingleFunctions | ILoadOptionsFunctions | IPollFunctions,
 	credentialType: OutlookCredentialType,
+	itemIndex: number,
 ): string | undefined {
 	if (credentialType !== 'microsoftEntraServicePrincipalApi') return undefined;
-	// Read at item index 0 (per-node constant, same as the `authentication` selector).
-	// loadOptions' getNodeParameter has no itemIndex arg (execute/poll do), so the
-	// { extractValue: true } overload can't be shared across all three contexts.
+	// loadOptions'/poll's getNodeParameter has no itemIndex arg (only execute does), so
+	// the { extractValue: true } overload can't be shared across all three contexts.
 	// Read the raw param and take the id-mode RLC value directly (this RLC has no
 	// extractValue regex, so .value is already the bare mailbox id).
-	const raw = this.getNodeParameter('mailbox', 0);
+	const raw = this.getNodeParameter('mailbox', itemIndex);
 	const value = isResourceLocatorValue(raw) ? raw.value : raw;
 	// A non-string or whitespace-only value collapses to '', which validateMailbox
-	// reports as the "mailbox required" error (not "not valid").
+	// reports as the "mailbox required" error (not "not valid"). A validation error
+	// gets its item index stamped in the router's catch.
 	const mailbox = (typeof value === 'string' ? value : '').trim();
 	validateMailbox(mailbox, this.getNode());
 	return mailbox;
 }
 
+// `itemIndex` is REQUIRED (and placed before the defaulted params so call sites
+// need no positional padding): execute call sites pass the loop index; non-execute
+// call sites (poll/loadOptions) pass a literal 0, where `getNodeParameter`'s 2nd
+// arg is a fallback, not an index.
 export async function microsoftApiRequest(
 	this: IExecuteFunctions | IExecuteSingleFunctions | ILoadOptionsFunctions | IPollFunctions,
 	method: IHttpRequestMethods,
 	resource: string,
+	itemIndex: number,
 	body: IDataObject = {},
 	qs: IDataObject = {},
 	uri?: string,
@@ -82,7 +89,7 @@ export async function microsoftApiRequest(
 			: 'https://graph.microsoft.com'
 	).replace(/\/+$/, '');
 
-	const mailbox = resolveMailbox.call(this, credentialType);
+	const mailbox = resolveMailbox.call(this, credentialType, itemIndex);
 
 	let apiUrl: string;
 	if (mailbox !== undefined) {
@@ -127,7 +134,7 @@ export async function microsoftApiRequest(
 			let updatedError;
 			// Try to return the error prettier, otherwise return the original one replacing the message with the description
 			try {
-				updatedError = prepareApiError.call(this, error);
+				updatedError = prepareApiError.call(this, error, itemIndex);
 			} catch (e) {}
 
 			if (updatedError) throw updatedError;
@@ -145,6 +152,7 @@ export async function microsoftApiRequestAllItems(
 	propertyName: string,
 	method: IHttpRequestMethods,
 	endpoint: string,
+	itemIndex: number,
 	body: IDataObject = {},
 	query: IDataObject = {},
 	headers: IDataObject = {},
@@ -160,6 +168,7 @@ export async function microsoftApiRequestAllItems(
 			this,
 			method,
 			endpoint,
+			itemIndex,
 			body,
 			nextLink ? undefined : query, // Do not add query parameters as nextLink already contains them
 			nextLink,
@@ -176,6 +185,7 @@ export async function downloadAttachments(
 	this: IExecuteFunctions | IPollFunctions,
 	messages: IDataObject[] | IDataObject,
 	prefix: string,
+	itemIndex: number,
 ) {
 	const elements: INodeExecutionData[] = [];
 	if (!Array.isArray(messages)) {
@@ -192,6 +202,7 @@ export async function downloadAttachments(
 				'value',
 				'GET',
 				`/messages/${message.id}/attachments`,
+				itemIndex,
 				{},
 			);
 			for (const [index, attachment] of attachments.entries()) {
@@ -199,6 +210,7 @@ export async function downloadAttachments(
 					this,
 					'GET',
 					`/messages/${message.id}/attachments/${attachment.id}/$value`,
+					itemIndex,
 					undefined,
 					{},
 					undefined,
@@ -226,12 +238,14 @@ export async function getMimeContent(
 	this: IExecuteFunctions,
 	messageId: string,
 	binaryPropertyName: string,
+	itemIndex: number,
 	outputFileName?: string,
 ) {
 	const response = await microsoftApiRequest.call(
 		this,
 		'GET',
 		`/messages/${messageId}/$value`,
+		itemIndex,
 		undefined,
 		{},
 		undefined,
@@ -259,6 +273,7 @@ export async function getMimeContent(
 export async function getSubfolders(
 	this: IExecuteFunctions | ILoadOptionsFunctions,
 	folders: IDataObject[],
+	itemIndex: number,
 	addPathToDisplayName = false,
 ) {
 	const returnData: IDataObject[] = [...folders];
@@ -269,6 +284,7 @@ export async function getSubfolders(
 				'value',
 				'GET',
 				`/mailFolders/${folder.id}/childFolders`,
+				itemIndex,
 			);
 
 			if (addPathToDisplayName) {
@@ -281,7 +297,12 @@ export async function getSubfolders(
 			}
 
 			returnData.push(
-				...(await getSubfolders.call(this, subfolders as IDataObject[], addPathToDisplayName)),
+				...(await getSubfolders.call(
+					this,
+					subfolders as IDataObject[],
+					itemIndex,
+					addPathToDisplayName,
+				)),
 			);
 		}
 	}