SquirrelMail "talks" several protocols.  To make sure that we are
standards-compatible, we need to refer to RFC documents.  Here's a list of
the ones we use a lot:

They are available from a wide variety of places on the net.
For instance, if you want RFC 822, you can jump directly to it at
    http://www.faqs.org/rfcs/rfc822.html
    http://www.rfc-editor.org/rfc/rfc822.txt
    http://www.imc.org/Searchable/rfc822

NUMBER     DESCRIPTION
-----------------------------------------------------------
RFC 1730   IMAP version 4
RFC 2060   IMAP version 4rev1
RFC 2183   Content-Disposition MIME header
RFC 2195   IMAP/POP AUTHorize Extension for Simple Challenge/Response
RFC 2298   Details return receipts
RFC 2342   The IMAP4 NAMESPACE command
RFC 2616   HTTP/1.1
RFC 2683   IMAP4 Implementation Recommendations
RFC 2822   Format of an email message (sendmail)
RFC 2831   Using Digest Authentication as a SASL Mechanism (digest-md5)
