psmtpd is a flexible smtpd daemon written in Perl. Apart from the core SMTP features, all functionality is implemented in small "extension plugins" using the easy to use object oriented plugin API.

qpsmtpd was originally written as a drop-in qmail-smtpd replacement, but now it also includes a smtp forward and a postfix "backend".

-- LucaGibelli - 10 Feb 2007