Scanning through Perl's CPAN archive, you will find numerous e-mail related modules. Probably 10 to 15 percent of all distributions are e-mail related. It is very hard to see which modules work together, and which module suites your needs best. Some are very old, some of very limited use, and some poorly written.
Let's first have a look at what features you need for e-mail processing, and then try to classify the main distributions.