The nnml spool mail format isn’t compatible with any other known format. It should be used with some caution.
If you use this back end, Gnus will split all incoming mail into files,
one file for each mail, and put the articles into the corresponding
directories under the directory specified by the
variable. The default value is ~/Mail/.
You do not have to create any directories beforehand; Gnus will take care of all that.
If you have a strict limit as to how many files you are allowed to store in your account, you should not use this back end. As each mail gets its own file, you might very well occupy thousands of inodes within a few weeks. If this is no problem for you, and it isn’t a problem for you having your friendly systems administrator walking around, madly, shouting “Who is eating all my inodes?! Who? Who!?!”, then you should know that this is probably the fastest format to use. You do not have to trudge through a big mbox file just to read your new mail.
nnml is probably the slowest back end when it comes to article
splitting. It has to create lots of files, and it also generates
NOV databases for the incoming mails. This makes it possibly the
fastest back end when it comes to reading mail.
Virtual server settings:
nnml directories will be placed under this directory. The
default is the value of
message-directory (whose default value
The active file for the
nnml server. The default is
nnml group descriptions file. See Newsgroups File Format. The default is ~/Mail/newsgroups.
nnml will read incoming mail. The default is
nil, this back end will ignore any NOV files. The
The name of the NOV files. The default is .overview.
Hook run narrowed to an article before saving.
nnml will allow using compressed message
files. This requires
auto-compression-mode to be enabled
(see Compressed Files in The Emacs Manual).
If the value of
nnml-use-compressed-files is a string, it is used
as the file extension specifying the compression program. You can set it
to ‘.bz2’ if your Emacs supports it. A value of
equivalent to ‘.gz’.
Default size threshold for compressed message files. Message files with
bodies larger than that many characters will be automatically compressed
nnml-use-compressed-files is non-
nnml groups and NOV files get totally out of
whack, you can do a complete update by typing M-x
nnml-generate-nov-databases. This command will trawl through the
nnml hierarchy, looking at each and every article, so it
might take a while to complete. A better interface to this
functionality can be found in the server buffer (see Server Commands).