AntiSpam
Allow POP users to use relay to send mail using a daemon that keeps an eye on the mail log and watches for POP3 logins on the machine.

Dynamic Relay Authorization Control
DRAC is a daemon that dynamically updates a relay authorization map for sendmail.

POP before SMTP
Patch for qpopper; sendmail configs and scripts for watching logfile.

Roaming
Extracts IP addresses from ipop3d syslog output for allowing roaming users to send mail through mail server; expires addresses after set time.

exim-pop-before-relay
A patch for Exim that adds a new lookup which checks spool files created by the popper.

pop-before-smtp
pop-before-smtp watches /var/log/maillog for lines written by UW popd/imapd describing successful login attempts, and installs entries for them in an on-disk hash (DB) that is watched by postfix. It expires the entries after a half-hour.

poprelayd
A system consisting of a single perl script and some Sendmail code.