I ran into an issue where newly created users within Active Directory
would synchronise incorrectly across to Office 365. The user would not
inherit the proper domain (contoso.com), but instead would have the
default domain (contoso.onmicrosoft.com). There are a few things to do
to resolve this:
- Make sure your domain has a UPN suffix for the email domain you wish
to use on office 365. In my case, my local domain (contoso.local)
is different to the external domain (contoso.com) we use email for.
I needed to add contoso.com as a UPN suffix for my domain.
- Instructions for doing this can be found here.
- You must then ensure that your user(s) are configured to use this UPN suffix. Please see the image below that shows where to choose the UPN when creating a new user.