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Issue with Sending Emails with Large Attachments via Graph API

Denys Soroka 71 Reputation points
2025-04-17T12:10:19.4+00:00

The current ability to send emails with large attachments via Graph API is broken for my tenant.

Reference: Large Attachments Documentation

An upload session URL returns a 401 Unauthorized error.

Steps to reproduce:

  1. Create a draft email via POST to the draft folder:
    POST /me/mailFolders('drafts')/messages -> 201
  2. Create an upload session:
    POST /me/messages/{messageid}/attachments/createUploadSession -> 201
  3. Attempt to upload:
    PUT {uploadUrl} -> 401

It is suspected that this issue is related to EX1026017, but no such error has been observed until today.

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  1. TA 135 Reputation points
    2025-04-18T19:18:14.3+00:00

    We finally received both confirmation from Microsoft of the issue as well as an update on the fix in our support ticket:

    The cause of the issue has been identified, and a fix has been rolled out. It is expected to be fully deployed by early next week. We apologize for the disruption this has caused.

    1 person found this answer helpful.

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