O365 Exchange sender domains restriction

Copper Contributor


I have problem how to setup restriction on Exchange online : " no e-mail from an unauthorized domain is allowed".
I tried it setup in Rules , but I dont see any possibility for these kind od restriction.

Thank you for any advice.

5 Replies


Hello! You've posted your question in the Tech Community Discussion space, which is intended for discussion around the Tech Community website itself, not product questions. I'm moving your question to the Exchange space- please post Exchange questions here in the future. 

What's an "unauthorized domain" though? You can configure domain-based whitelist/blocklist as detailed here: https://docs.microsoft.com/en-us/microsoft-365/security/office-365-security/configure-your-spam-filt...
Hello Vasil, "unauthorized" means for example: only emails from domains MyCompany1.xx and MyCompany2.xx are allowed as senders to my Exchange.
I tried setup allowed domains in anti-spam inbound policy , but this policy is focused to skip alowed domains from anti spam procedures.
If the idea is to only allow messages from specific domains, best use Mail flow rules, where you can add those domains as "exceptions".
YES, Thank you very much Vasil, sometimes the things are simple ...
Good luck