You may also have configured mutt to co-operate with Mixmaster, an anonymous remailer. Mixmaster permits you to send your messages anonymously using a chain of remailers. Mixmaster support in mutt is for mixmaster version 2.04 (beta 45 appears to be the latest) and 2.03. It does not support earlier versions or the later so-called version 3 betas, of which the latest appears to be called 2.9b23.
To use it, you'll have to obey certain restrictions. Most
important, you cannot use the Cc and Bcc headers. To tell
Mutt to use mixmaster, you have to select a remailer chain, using
the mix function on the compose menu.
The chain selection screen is divided into two parts. In the (larger) upper part, you get a list of remailers you may use. In the lower part, you see the currently selected chain of remailers.
You can navigate in the chain using the chain-prev and
chain-next functions, which are by default bound to the left
and right arrows and to the h and l keys (think vi
keyboard bindings). To insert a remailer at the current chain
position, use the insert function. To append a remailer behind
the current chain position, use select-entry or append.
You can also delete entries from the chain, using the corresponding
function. Finally, to abandon your changes, leave the menu, or
accept them pressing (by default) the Return key.
Note that different remailers do have different capabilities, indicated in the %c entry of the remailer menu lines (see $mix_entry_format). Most important is the ``middleman'' capability, indicated by a capital ``M'': This means that the remailer in question cannot be used as the final element of a chain, but will only forward messages to other mixmaster remailers. For details on the other capabilities, please have a look at the mixmaster documentation.