added an accepted domain to exchange server, but cannot choose it as a logon domain when creating email addresses?
As Shane has mentioned, it’s a bit different. I do think it’s generally a good idea to have UPNs match up to email addresses though as it makes users’ lives easier (I fight for the users). So if you’d like to do that, add it as a UPN suffix for the forrest. There is a Microsoft kb243629 article.
Here’s a basic recap of the KB article:
1)Open Active Directory Domains and Trusts.
2)Right-click Active Directory Domains and Trusts in the Tree window pane, and then click Properties.
3)On the UPN Suffixes tab, type the new UPN suffix that you would like to add to the forrest.
4)Click Add, and then click OK
Once that’s done, you may add user accounts with the UPN suffix you desire.