Can't receive but can send email after exchanging computers on LAN.

Setup: OS X Server running on Mac Mini, with mostly iMacs/Macbooks on the LAN, but one PC (Windows 7). All services, including Email and Open Directory, were running fine. All users are Local Network Users.

Problem: last week two users switched their computers, i.e., PC user transferred to one of the iMacs and the iMac user transferred to the PC. The PC user is sending/receiving their email just fine, but the Mac user can only send email (can't receive any).

Is the optimal fix to delete the Mac user's account from the Users list in the OS X Server, and then recreate it? If so, what steps should I take to preserve the emails already in the account ?

Ron Goebel