When you select a message from the index and view it in the pager, Mutt
decodes the message to a text representation. Mutt internally supports
a number of MIME types, including text/plain, text/enriched,
message/rfc822, and message/news. In addition, the export
controlled version of Mutt recognizes a variety of PGP MIME types,
including PGP/MIME and application/pgp.
Mutt will denote attachments with a couple lines describing them. These lines are of the form:
[-- Attachment #1: Description --]
[-- Type: text/plain, Encoding: 7bit, Size: 10000 --]
Description is the description or filename given for the
attachment, and the Encoding is one of
7bit/8bit/quoted-printable/base64/binary.
If Mutt cannot deal with a MIME type, it will display a message like:
[-- image/gif is unsupported (use 'v' to view this part) --]