One of our clients is sending us email messages as Word document with macros as .docm files. Firstly we run into problem that my users are not receiving files of that type. The problem was solved by creating a custom Anti-Malware policy with .docm files being enabled and applying it to an AD group. This works fine and the recipients are now able to receive and open these files.
Now we have a problem that we cannot send these files back to the customer and generally to any recipient outside the organization . Messages are being delivered, but the attachments are being replaced with a text file with the name “Unsupported File Types Alert.txt”. If you open the text file, you can read “This message was quarantined as malware.”
Please note, the problem is related to outbound messages, which we send to outside.
We have our mailboxes in Exchange-Online and using Microsoft® Outlook® für Microsoft 365 MSO (Version 2109 Build 16.0.14430.20292) 64 Bit
Since hours I am trying to find a solution, but without success. I hope someone has an idea :smiling_face_with_smiling_eyes:
I hope this will help in case somebody else runs in the problem. The solution was to enable (uncheck) corresponding attachment in the default Anti-Malware policy. The custom Anti-Malware policy we have created to allow the attachment have no effect on outgoing messages.