Excel attachment replaced by a TXT file - Hybrid with Exchange Server 2013

Question

Hello,
I have a Hybrid environment with Exchange Server 2013 with 2 Sites of Exchange Servers.
An internal application, only with email address without a mailbox, sends email with Excel file (XLSX extension) attached to internal recipients and the emails are being received with a replaced TXT file and inside there is the "This attachment was removed.".
I already tracked the messages and I did not find any relevant information.
I don't have any filter on Exchange Servers, no antivirus for email is installed.
Is there any command to check this?

Thank you.

Answer 1

Hi @Luizg_mg

Where are the recipients located, on-premise or online?

Does it happen with other file types?

You may check if the issue is caused by Exchange Online Malware Filters. Go to Exchange Online Admin Center > Protection > Malware Filter, and check the policies there. Under their settings, check Common Attachment Types Filter list to see if the corresponding extension (which is .xlsx in this case as you mentioned) is listed there. If so, which I highly suspect it is, remove that file type from that list to prevent it from being blocked.

The Common Attachment Types Filter

If the message is sent to on-premise users, consider using Pipeline tracing to check what changed the message

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