Antimalware policy

Question

We have a default antimalware policy that blocks attachments based on their extensions. However, we’ve noticed some unusual behavior.

We added .z to the policy, and it unexpectedly started blocking .zip files. However, this issue is not affecting all users—only a few are experiencing the block. There are no other rules explicitly blocking .zip files.

It’s unclear whether the policy is occasionally malfunctioning. Any insights or suggestions on this?

Answer 1

Hi @Vishnu Anand,

Thank you for posting your question in the Microsoft Q&A forum.

As per your description, your issue is with the .z policy in the anti-malware policy affecting the .zip policy.

First of all I would like to know whether your exchange environment is on-premises or online, which will help us to analyze the issue further. For the current information, there are a few suggestions below that I hope will help you.

1. Retest the affected users to see if the .zip files are all blocked. If the problem persists, please perform the following tests.
2. Try temporarily removing the .z policy from the policy and test if the affected users are back to normal. If they do not return to normal, then something else is blocking the .zip file, and it is not the new policy.
3. Check the Message tracking logging, which is a detailed record of all mail activity as it flows through the transport pipeline on the Exchange server, to help you analyze the cause of the block.

If the answer is helpful, please click on “Accept answer” as it could help other members of the Microsoft Q&A community who have similar questions and are looking for solutions.

Thank you for your support and understanding.