Next: Mail Sources, Previous: Getting Started Reading Mail, Up: Getting Mail

#### 6.4.3 Splitting Mail

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.