pgl4rbl implements a Postfix policy server that mixes two widely used techniques: greylisting and RBL (DNS blacklists). The idea is that greylisting is applied only to SMTP clients that match a RBL; this means that normal clients are not delayed (such as with a normal greylisting implementation), and RBL false positives do not cause problems (like when outright blocking them at the SMTP level).
ChildProt is a child protection policy daemon for Postfix. It checks a list of recipient addresses. If the current recipient address is found, the sender address is verified against a whitelist. If the current sender address is found, the mail will be delivered to the recipient. If the sender address is not found on the whitelist, the mail will be redirected to a delegate of the recipient. If the recipient address is not found the mail will be delivered to the recipient too.
vmm is an easy-to-use and configurable commandline tool for administrators and postmasters, used to manage domains, alias-domains, accounts, and relocated mail users. It allows fast and easy management of mail servers. It's designed for installations using Dovecot and Postfix with a PostgreSQL backend.
POP-Before-SMTP-Auth is a POP before SMTP daemon for Dovecot and Postfix that works by scanning mail server log files. The line-matching regex can be changed from the configuration file, in case Dovecot's logging format changes, and also to adapt the script for use with something besides Dovecot. Presently the script requires that the IP address appear on a single line with the successful login in the log file.
checkMX is a Perl daemon which monitors remote MX servers for a domain's overall health. If all the MX hosts are down and the domain can no longer receive mail, checkMX updates the Postfix relay_domains file so it will start accepting mail for the broken domain. Once the domain can start accepting mail on its own, checkmx will flush the mail queue for delivery and remove it from postfix relay_domains file. This prevents spammers from using the backup MX server as a spam vector.