pop3 attachment decoding

[HyperChris at aol.com]

I am playing with the 'POP library' stack (thank you and kudos to Sarah) and 
it's time to decode the attachments. I can write my own decodes for the easy 
ones, like TXT and HTML, but I would like to better understand the format and 
do something that could be reused by others. Has anyone already done this ? 
And/or know which RFC defines the standard ?   Thank you ... Chris