Good night, everyone. When an email with attachments is forwarded to me, for example from Thunderbird or Sogo, outlook detects that it has attachments, but does not show them. If you send me a new file and attach files, I can see it, but not if it is forwarded. From Sogo I can see the attachments or from another email client (IOS, Android) as well. The Outlook versions we have are 2021. Any idea what the problem could be? Thank you very much

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You mean that happens from within mailcow? No external mail involved?

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Scenario: A user with an account in my domain sends an email with attachments to another user from my domain. This user has Thunderbird and sends the email with attachments to another user who has Outlook 2021. In this case the user with Outlook does not see the attachments (he can see them from Sogo or mobile). Thanks !!

You know that Outlook blocks by default some file types based on extension or mime type?
have you tried to send something “neutral” like a PDF as attachment?

I just have tried your scenario, and with my Outlook 2021 (via Activesync) I get the attachment sent by Thunderbird.

Yes, I have tried pdf,xls and zip. I’ll see if I have any Office suite updates pending. The problem must surely be there. I’ll let you know the result when I try it. Thanks boss

6 days later

Hi @esackbauer

I have performed several tests.

  • If I send a new email from ThunderBird to Outlook, I DO see the attachments.
  • If I forward a mail with attachments from Thunderbird to Outlook, the attachments are not seen.
  • If I forward a mail and add attachments they do not appear in Outlook either.

In any mail client other than Outlook 2021 I do see the attachments.

I have tried to send xls, zip, pdf…. In plain or html format

I just tried it with my Setup:
Sending from Thunderbird 128 on Linux Mint
Receiving on Microsoft® Outlook® für Microsoft 365 MSO (Version 2402 Build 16.0.17328.20550) 64 Bit

All 3 tests you mentioned are working. I can see the PDF attachment properly in each case.

Later I will do some tests again with my Outlook 2021 (non-MS365) and post the results and exact version number.

Have you tried it with opening Outlook in support.microsoft.com Icon safe mode

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Sending from Thunderbird 131 beta on Windows 10
Receiving on Microsoft® Outlook® 2021 LTSC MSO (16.0.14332.20788) 32-Bit

All 3 tests you mentioned are working. I can see the PDF attachment properly in each case.

So please check in safe mode as written above, probably its an add-in which causes this or a group policy.

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