I'm quite the newbie, but the easiest way I've found to make configuration changes (from a gui) is via webmin (www.webmin.com
). Not only can you make Sendmail configuration changes, but you can make changes to your firewall for the ports in question.
I'm still running the Sendmail build that came with Red Hat 9. I don't have the hang of patching, installing, etc. ... yet.
For Red Hat, I read a post about enabling POP3. All you had to do was go to the "ipop3" file, change "disable" to "no" and restart "xinetd". Of course, you still have to open the FW for POP. No, I haven't tested this yet.