In addition to explicitly telling Mutt to view an attachment with the MIME viewer defined in the mailcap file, Mutt has support for automatically viewing MIME attachments while in the pager.
To work, you must define a viewer in the mailcap file which uses the
copiousoutput option to denote that it is non-interactive.
Usually, you also use the entry to convert the attachment to a text
representation which you can view in the pager.
You then use the auto_view muttrc command to list the
content-types that you wish to view automatically.
For instance, if you set auto_view to:
auto_view text/html text/enriched application/x-gunzip application/postscript image/gif application/x-tar-gz
Mutt could use the following mailcap entries to automatically view attachments of these types.
text/html; lynx -dump %s; copiousoutput; nametemplate=%s.html
text/enriched; enriched.sh ; copiousoutput
image/*; anytopnm %s | pnmscale -xsize 80 -ysize 50 | ppmtopgm | pgmtopbm | pbmtoascii ; copiousoutput
application/x-gunzip; gzcat; copiousoutput
application/x-tar-gz; gunzip -c %s | tar -tf - ; copiousoutput
application/postscript; ps2ascii %s; copiousoutput
``unauto_view'' can be used to remove previous entries from the autoview list. This can be used with message-hook to autoview messages based on size, etc. ``unauto_view *'' will remove all previous entries.