HOW TO FORCE REMOVE contoso.ONMICROSOFT.COM MAIL ALIAS ?

[Marvin Oco]

HI,

HOW TO FORCE REMOVE .ONMICROSOFT.COM MAIL ALIAS?

the mail that should remain is contoso.com

users are synched from local AD.

thanks

[#2]

@Marvin Oco Generally it's a bad idea to touch the onmicrosoft.com aliases and other references, Microsoft uses these under the hood for many different purposes. When you're using Azure AD Connect, it will probably even prohibit you from removing it.

So what's the exact use case here? If the user's primary proxy address is set to their "@contoso.com" address but they have a secondary alias set to their onmicrosoft.com address, is this a concern or problem? Did something break?

[#3]

to prevent external senders to send to .onmicroft.com alias

[#4]

Makes sense I guess. As mentioned, I seem to recall you cannot really remove these in a hybrid identity situation. You could leave them in place and reject all external email directly sent to the onmicrosoft.com domain as an alternative option. There’s an old article at the link below, not sure if it’s still applicable nowadays but a quick scan through it seems it should be.

https://docs.microsoft.com/en-us/archive/blogs/rrajan/how-to-block-direct-delivery-to-email-address-...