Exchange 2010 in an old environment

Question

Lets preference this with I am by no means an Exchange administrator.

I have an old domain (2003) that I inherited and am in the process of moving to 2019. My issue is with Exchange 2010 connectivity. I have an older version of exchange 2k3. I now have 2012r2 DCs and the domain functional level is 2008R2. I still have some old XP boxes and am deploying new WIN10 boxes.

I installed Exchange 2010 and was able to move all but two mailboxes to the new database. Which is another story.
The current issue is that my general user accounts can not log into email on either the XP or WIN10 PCs. When they click on Outlook the mail profile starts to initialize they get to the screen that shows exchange server and email address and when you click next it asks for the users password. If you enter the password the window for password entry keeps coming back up and if you hit cancel the mail profile screen just sits there until you cancel.

Nothing shows up in logs either on workstation or Exchange server.
OWA attempts give unknown username or access denied.
Admin accounts have no issues

I have been scouring the forums for days trying to find a fix.

Help would be appreciated thanks.