Documentation for how to allow email forwarding from an MS365 email account
Go to mail tab of a user profile
Click on the forwarding option
At the top where it has a warning letting you know that you won’t be able to actually send out mail click on “manage outbound anti-spam policies”
on the anti-spam policies page within defender click anti-spam outbound policy
then click edit protection settings
near the middle of the page is one labeled forwarding rules, and it’ll say automatic forwarding rules if it’s on system, default or off, it will block all forwarding
when you change it “on” you will get an error message saying that certain things must be set up, click OK
then you have to wait roughly 72 hours for these things to take affect. there is a method where you submit a ticket to Microsoft and they run a ton of power shell commands to try to accelerate the process but the most reliable methodology I have found is just waiting the time that they say.
there is not an indicator or progress bar or confirmation email once the changes have applied
here’s the key part: once the tenant update has happened that allows for external email forwarding, that rule will go back to system default. you now have to open back up that anti-spam policy and change it back to the “on” position.
then you can go to any person’s email within the users, directory page, put in forwarding and put in some address completely outside of the domain. Send it a test email from something completely outside the domain, and once you see that confirmation email come through. You are all set!