Subdomain - Shared Mailbox Alias

Regular Contributor

Hi all,

I setup a sub domain e.g.

When I create a shared mailbox e.g. test @ it will get an alias of test @ and test @ is the primary domain name. I'm guessing there's a default policy that adds this alias? Is there anyway to prevent it from happening?


It doesn't seem to happen for a user account with the sub domain, just the shared mailbox.

2 Replies
best response confirmed by David Gorman (Regular Contributor)
There is a "requirement" in Office 365 that at least one SMTP address matches the value of the UPN, so make sure you set the UPN to Email address removed as well.

Thanks @Vasil Michev 


The UPN would be the primary domain -


As there's no way to set this in the Office 365 website, it just looks for an email address, can I change the UPN of test @ in Powershell, do you know?


Ah - I can change this Powershell. Now to test it works correctly. Cheers!


It would be useful to be able to do this from the web version though.