Currently I\'m using the PEAR library\'s mimeDecode.php for parsing incoming emails. It seems to have a lot of issues and fails to decode a lot of messages, so I\'d like to
Funny you should ask... Im actually working on a simple notification system now. I just finished up the Bounce Manager with i use Zend_Mail to implement. It has pretty much all the features you're looking for... you can connect to a mailbox (POP3, IMAP, Mbox, and Maildir) and pull messages from it as well as operate on all those messages.
It handles multipart messages, but the parts can be hard to work with. I had a hard time figuring out which part was the attached original message part in the NDR's I was working with, but I have a feeling I just missed something in the documentation. I'm not sure how it handles encoding, because my usage was fairly simple but I'm pretty sure it has provisions for all the encodings you mentioned. Check out the docs and browse the API.