MailAttachmentAdd

Summary

• Adds a small file attachment to an existing message (draft or sent).

Graph Endpoint

• POST /me/messages/{messageId}/attachments

Parameters

Required

• messageId: string — Alias: id

• One of:

  • attachmentIds: number[] — Up to 10 repository attachment IDs; backend fetches file data and uploads it.

  • name: string and contentBytesBase64: string — Direct upload of a single file (alias: contentBase64).

Optional

• contentType: string — Default application/octet-stream

Usage (app.businessFunction)

Using repository attachments (recommended)

app.businessFunction({
  functionName: 'MicrosoftGraph',
  methodName: 'Mail',
  operation: 'AttachmentAdd',
  parameters: {
    messageId: 'AAMkAGI2N...',
    attachmentIds: [1012, 1013] // up to 10
  }
})

Single file (base64)

app.businessFunction({
  functionName: 'MicrosoftGraph',
  methodName: 'Mail',
  operation: 'AttachmentAdd',
  parameters: {
    messageId: 'AAMkAGI2N...',
    name: 'report.pdf',
    contentBytesBase64: 'JVBERi0xLjQKJc...'
  }
})

Response

// When using attachmentIds
{ "ok": true, "attachments": [ { "id": "...", "name": "..", "size": 123456, "contentType": "application/pdf" } ] }

// When uploading a single base64 file
{ "ok": true, "attachment": { "id": "...", "name": "report.pdf", "size": 123456, "contentType": "application/pdf" } }

Notes

• Backend uploads via upload sessions (robust for any size). Limit: max 10 attachments per call when using attachmentIds.

• For external clients without repository attachments, use the base64 single-file option or MailAttachmentUploadLarge.

See also

• MailSend — send a new message with attachmentIds in one call

• MailReply — reply and attach repository files

• MailReplyAll — reply-all with attachments

• MailForward — forward with attachments