This happens to me frequently when I change roms - out of curiousity did you use sprite backup to restore your info? I am on ATT and even though settings = proxy disabled/smtp server=cwmx.com/no authentication and haven't changed, my account will recieve email, but not send... I have also had some problems with some corporate emails when I try to reply, but not if I initiate the email myself (wtf?)
The solution for me was to delete the email account from the account picker and then click on new email account icon & enter all the info again for the same account - a PITA but it hasn't failed me yet.
If someone has a simpler solution I would be ecstatic.
NotATreoFanV5 ATT Manilla