When I read the e-mail in root's mail, it says both the sender and the receiver are named Unknown. I have set up user accounts successfully. My POP is working, as I am able to use telnet successfully with POP, but I cannot get POP-3 to work properly. When a user tries to retrieve their mail, nothing is coming through. When retrieving mail with POP, mail is read from that location and transferred to the user's home directory, appending the message to the file mbox .
POP actually reads the mail from mbox in the user's home directory.
The user name and passwords must be correctly set up for remotely logging into the Linux machine. Maybe it is worth mentioning that you need to have the POP service installed through the IMAP RPM on a Red Hat system. If this is correctly set, you should be able to retrieve mail from the server from the PCs. For Internet e-mail from the PCs through the server, Sendmail has to be correctly configured as well according to your external connection parameters. I think you may have a setup problem with your domains.