+RFC 822 Format of ARPA Internet text messages
+RFC 1730 IMAP version 4 (obsoleted by 2060)
+RFC 2045 MIME Part One: Format of Internet Message Bodies
+RFC 2046 MIME Part Two: Media Types
+RFC 2047 MIME Part Three: Message Header Extensions for Non-ASCII Text
+RFC 2060 IMAP version 4rev1 (obsoleted by 3501)