Yes, Blitz supports TCP and POP3 is a TCP protocol. Attachments are simply separate sections of the message body separated by MIME codes; when forwarding, you don't need to decypher the body - you can just send the entire body, which will include attachments.
There might be some POP3 code in the archive. If not, here's the RFC on POP3:
http://www.google.com/search?q=pop3+rfc&btnI=I'm+Feeling+Lucky
There might be some POP3 code in the archive. If not, here's the RFC on POP3:
http://www.google.com/search?q=pop3+rfc&btnI=I'm+Feeling+Lucky