Pop3 Episode 2: Mime Type strategy?

Question

Okay, so let's say I have a message fetched from a pop3 server.

What I ultimately want to do is to put it in its corresponding user's mailbox, which is an XML file. For the headers, I managed something good already, so I don't need to think about it, I have to do the message body's part.

How should I process the file?

For now, my logic would be

For retrieval:
  Go get the mime types (multipart or not) and build a hierarchy 
  of items and subitems, or something.

For display:
   1. Check the mime type
      1a - Is Multipart:
        Go to the boundary and check the mime type.
        If is multipart, fire 1a again, with this boundary instead.
      1b Is text/plain
          Format using endlines
      1c Is text/html
          Don't bother with formatting, strip dangerous stuff.