Major Outlook issue prevents sending emails with attachments

Martin Brinkmann
Nov 8, 2023
Microsoft Outlook

Microsoft confirmed an issue yesterday that prevents the sending of emails with attachments. The company notes in an advisory that affected users are unable to send emails that contain attachments.

Affected users see the message "Error code 550 5.7.520 Message blocked" when they are impacted by the issue according to Bleeping Computer.

Microsoft suggests two workarounds for affected users while it is fixing the problem. Outlook users may upload the file attachments to OneDrive to attach links that point to these files to their Outlook emails.

outlook attachment

To do so, Outlook users may follow these steps in the email client:

  1. Create a new email message, reply to an existing one or forward an email message.
  2. Select the attach file option in the compose window.
    1. If the file is hosted on OneDrive already, select OneDrive.
      1. Pick the files on OneDrive and select Share link to add them to the email.
    2. If the file is on the local computer, select Upload and share instead.
      1. Use the file browser to upload the file to OneDrive. The file is added to the email automatically.

The process adds a link to the email address only. It contains a link to, which Microsoft uses to shorten links of OneDrive attachments. You can hover over the attached link in the email to see the full address.

outlook attached link onedrive

The second workaround that Microsoft suggests is to copy links of Office or OneDrive files directly to paste them into the email.

Naturally, users may also use any other file host on the Internet, e.g., Dropbox or Google Drive, for the workaround. Just upload files that you want to attach to emails to these services and use the share feature for these links to create a link that you then add to the email in Outlook.

Microsoft offers no additional information on the issue. The number of affected users is unknown. It is also unclear if Outlook users who use a dedicated email client are affected by the attachment issue.

The company continues its work on the new Outlook for Windows application that will replace the classic Mail and Calendar apps eventually. Not all Windows users are happy with the change, as the new app is just a progressive web app and not a dedicated application. This article compares the functionality to the classic Outlook app.

Now You: do you use Outlook?

Major Outlook issue prevents sending emails with attachments
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Major Outlook issue prevents sending emails with attachments
Microsoft confirmed an issue yesterday that prevents the sending of emails with attachments.
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  1. El Barsko said on November 8, 2023 at 3:12 pm

    I like Mail and Calendar better, much better.
    El Barsko

    1. bruh said on November 8, 2023 at 6:17 pm

      End user moment, Outlook is used in the “””professional””” sphere, of course it won’t appeal to you.

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