ok I have some domains setup. All is working.
But The email gets rejected if it sent to firstname.lastname@example.org
it goes through if it is email@example.com
How do I make it so both are valid?
Can you paste in the exact error you're getting?
And, is mail.abc.com setup as a Virtual Server on your system?
Also, what is your server's hostname... is that different than mail.abc.com?
Lastly -- if you go into System Settings -> Re-Check Config, do you see any problems?