Mutt recognizes four FolderFormat""s. If a folder is correct by any
of those formats' standard, then mutt can automatically read them,
nothing needs to be done just for reading. However, when you create new
folders (MuttFaq/Action), the format used is specified via
See OverloadedNames for clarification of the various uses of "mbox" and
An mbox folder is a plain text file. Each message starts with a "From "
line (note the trailing space). For example:
`From email@example.com Fri Jun 23 02:56:55 2000`
Body-lines starting with "From" are usually escaped as ">From" if they
occur in messages, but there is also a header "Content-Length:" that
gives the number of lines in the message so that From escaping is not
necessary. Mutt supports all formats.
A maildir folder is a directory with exactly three subdirectories
"new", "cur", and "tmp". Each message is a separate file. See
MaildirFormat for details.
An MH folder is a directory containing either a .mh_sequences or
.xmhcache file. Messages are separate files that are numbered
sequentially. MH is rarely used, most prefer the maildir format.
This is a variant of the mbox format. Each message is surrounded by
lines containing "^A^A^A^A" (four control-A's). Using this format is not
recommended, few other programs support it.
Which format to use?
Don't use MH or MMDF, as these are not widely supported by other
programs. Whether to use mbox or maildir is a matter of taste. mbox is
sometimes easier to handle because it is just a single file, whereas
with maildir you don't need to read the whole folder just to get a
single message. The rest is philosophy, a big source of flamebaits, and
an endless quest for the best way to benchmark it. Maybe MuttFaq/Maildir
can help you out.
If you happend to choose either MH or Maildir, you can improve
performance by using header caching, see MuttGuide/Caching for details.