Far and away our most-popular product, MIME::Lite is a simple standalone Perl module for generating MIME messages: you can use it to create and send email messages with text or binary attachments. It takes care of all the encoding for you.
Note that this module does not parse messages... for that, you need MIME-tools.
MIME::Lite is now being maintained by Yves Orton. We pass our software on to others when we feel they can do a better job maintaining and extending it than we can — it keeps good code from becoming obsolete.