How to unblock a specific file extension - exchange online

Aran Billen 741

Hi all,

How do I allow a specific file type which is being blocked by exchange online:

Screenshot 2024-06-27 at 10.48.30

1 answer

Vasil Michev 98,946 Reputation points MVP

2024-06-28T06:10:35.2633333+00:00

You will have to modify the Anti-malware policy to allow the file type, as detailed here: https://video2.skills-academy.com/en-us/defender-office-365/anti-malware-protection-about#common-attachments-filter-in-anti-malware-policies

In addition, you have to unblock the filetype in the OWA Mailbox policy assigned to the user(s) in question. You can only do this via PowerShell and the Set-OWAMailboxPolicy cmdlet: https://video2.skills-academy.com/en-us/powershell/module/exchange/set-owamailboxpolicy?view=exchange-ps
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Aran Billen 741 Reputation points

2024-06-28T09:12:57.4966667+00:00

Thank you. I have added it however still getting blocked, does it just take time to take affect?

Vasil Michev 98,946 Reputation points MVP

2024-06-28T15:14:46.3266667+00:00

It should work in an hour or so. Keep in mind that this policy only applies to the webmail (OWA), if you use any other client it will not work. I.e. for Outlook desktop client, there is a separate procedure: https://support.microsoft.com/en-us/office/blocked-attachments-in-outlook-434752e1-02d3-4e90-9124-8b81e49a8519
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