Windows 2012 AD Environment
In order to prep for O365, we recently change everyones UPN to match their PrimarySMTPAddress.
Not changing their User Logon Name (pre-Windows 2000), that stayed the same.
About 90% of the users are still able to log in using their Pre-Windows 2000 logon names and/or new UPN (email address), but there are reports coming in that many can not log in.
Anyone know what I could be looking for to troubleshoot? Thinking it could be AD replication perhaps? depending what global catalog server they may be hitting?