Message is
a MIME-compliant posting agent. The user
generally doesn't have to do anything to make the
MIME happen—Message will automatically
add the Content-Type and
Content-Transfer-Encoding headers.
The most typical thing users want to use the multipart things in MIME for is to add “attachments” to mail they send out. This can be done with the C-c C-a command (M-x mml-attach-file), which will prompt for a file name and a MIME type.
If your Emacs
supports drag and drop, you can also drop the file in the Message
buffer. The variable mml-dnd-protocol-alist
specifies what kind of action is done when you drop a file into
the Message buffer. The variable
mml-dnd-attach-options controls which
MIME options you want to specify when dropping
a file. If it is a list, valid members are type,
description and disposition.
disposition implies type. If it is
nil, don't ask for options. If it is t,
ask the user whether or not to specify options.
You can also create arbitrarily complex multiparts using the MML language (see Composing).