this is the rdbms you have in your back pocket....good enough for small apps, bindings in many languages, fast and easy to use/maintain/install. it just doesn't get any better.
if you have no interest in leaving perl for ruby but want the ease of use that rails brings to developing webapps thru MVC, then catalyst is for you. it's written by some top-tier perl programmers.
the cpan installations have a lot of dependencies so prepare to update your perl with a lot (no, i mean a lot) of packages from the cpan. after that's done though, developing with catalyst and running it on apache is a cakewalk.
qmail has the patches needed to bring it inline with what a modern mail server needs. it is very actively developed from a patch standpoint. the qmail mailgroup hosted by the author is very, very active.
first off: forget sendmail and exim, just too buggy, bloated and insecure.
the only competition is with qmail and postfix. compare LOCs and the number of serious security bugs and qmail is the winner.
Sometimes the simplicity of DJB's software trips people up. There are no complicated zone files or configurations in XML; in his signature style, djb uses directories and files to configure the software. A lot of folks don't realize how utterly elegant and simple this is....I admit, getting a summary of the config takes a little effort (ala script or a 3rd party front-end), but the configs are so easy to manipulate b/c it is just dir/file/content and easy to automate or hand edit.
djbdns is, hands down the most secure dns system out there - it is also light on system resources and performs very very well. Germany is using them to host their root nameservers and many fortune 500 companies use djbdns for their externally hosted dns for security reasons.
Read djb's setup guidance and join the list at his site. If you still have trouble, check out lifewithdjbdns