Preventing external senders from emailing internal Office 365 groups

This recipe will cover how an admin can prevent external parties from emailing internal Office 365 groups, which can have their own email address and shared mailbox.

Getting ready

You must be a global admin to perform these steps.

How to do it…

Update the -Identity parameter with the display name of the group you wish to change, and then run the following code snippet:

Set-UnifiedGroup -Identity "Test" -RequireSenderAuthenticationEnabled $true

How it works…

You've just protected an Office 365 group's inbox from unwanted external emails. Setting the -RequireSenderAuthenticationEnabled property on a group allows only internal users to send an email to that group. If external users send a message to the group's email address, that message will be rejected. Internal users are still able to send externally, unless other restrictions are put in place.

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