The
nnmail-split-methods variable says how the incoming
mail is to be split into groups.
(setq nnmail-split-methods
'(("mail.junk" "^From:.*Lars Ingebrigtsen")
("mail.crazy" "^Subject:.*die\\|^Organization:.*flabby")
("mail.other" "")))
This variable is a list of lists, where the first element of
each of these lists is the name of the mail group (they do not
have to be called something beginning with
‘mail’, by the
way), and the second element is a regular expression used on the
header of each mail to determine if it belongs in this mail
group. The first string may contain ‘\\1’ forms, like the ones used by
replace-match to insert sub-expressions from the
matched text. For instance:
("list.\\1" "From:.* \\(.*\\)-list@majordomo.com")
In that case,
nnmail-split-lowercase-expanded controls whether the
inserted text should be made lowercase. See Fancy Mail
Splitting.
The second element can also be a function. In that case, it
will be called narrowed to the headers with the first element of
the rule as the argument. It should return a non-nil
value if it thinks that the mail belongs in that group.
The last of
these groups should always be a general one, and the regular
expression should always be ‘""’ so that it matches any mails that
haven't been matched by any of the other regexps. (These rules
are processed from the beginning of the alist toward the end. The
first rule to make a match will “win”, unless you
have crossposting enabled. In that case, all matching rules will
“win”.) If no rule matched, the mail will end up in
the ‘bogus’
group. When new groups are created by splitting mail, you may
want to run gnus-group-find-new-groups to see the
new groups. This also applies to the ‘bogus’ group.
If you like to tinker with this yourself, you can set this variable to a function of your choice. This function will be called without any arguments in a buffer narrowed to the headers of an incoming mail message. The function should return a list of group names that it thinks should carry this mail message.
This variable can also be a fancy split method. For the syntax, see Fancy Mail Splitting.
Note that the mail back ends are free to maul the poor,
innocent, incoming headers all they want to. They all add
Lines headers; some add X-Gnus-Group
headers; most rename the Unix mbox From<SPACE>
line to something else.
The mail back ends all
support cross-posting. If several regexps match, the mail will be
“cross-posted” to all those groups.
nnmail-crosspost says whether to use this mechanism
or not. Note that no articles are crossposted to the general
(‘""’)
group.
nnmh and nnml
makes crossposts by creating hard links to the crossposted
articles. However, not all file systems support hard links. If
that's the case for you, set
nnmail-crosspost-link-function to
copy-file. (This variable is
add-name-to-file by default.)
If you wish to see
where the previous mail split put the messages, you can use the
M-x nnmail-split-history command. If you wish to see
where re-spooling messages would put the messages, you can use
gnus-summary-respool-trace and related commands (see
Mail Group
Commands).
Header
lines longer than the value of
nnmail-split-header-length-limit are excluded from
the split function.
By
default, splitting does not decode headers, so you can not match
on non-ASCII strings. But it is useful if you
want to match articles based on the raw header data. To enable
it, set the nnmail-mail-splitting-decodes variable
to a non-nil value. In addition, the value of the
nnmail-mail-splitting-charset variable is used for
decoding non-MIME encoded string when
nnmail-mail-splitting-decodes is
non-nil. The default value is nil which
means not to decode non-MIME encoded string. A
suitable value for you will be undecided or be the
charset used normally in mails you are interested in.
By default,
splitting is performed on all incoming messages. If you specify a
directory entry for the variable
mail-sources (see Mail Source
Specifiers), however, then splitting does not happen
by default. You can set the variable
nnmail-resplit-incoming to a non-nil
value to make splitting happen even in this case. (This variable
has no effect on other kinds of entries.)
Gnus gives you all the opportunity you could possibly want for shooting yourself in the foot. Let's say you create a group that will contain all the mail you get from your boss. And then you accidentally unsubscribe from the group. Gnus will still put all the mail from your boss in the unsubscribed group, and so, when your boss mails you “Have that report ready by Monday or you're fired!”, you'll never see it and, come Tuesday, you'll still believe that you're gainfully employed while you really should be out collecting empty bottles to save up for next month's rent money.