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6.4.6 Fancy Mail Splitting

If the rather simple, standard method for specifying how to split mail doesn't allow you to do what you want, you can set nnmail-split-methods to nnmail-split-fancy. Then you can play with the nnmail-split-fancy variable.

Let's look at an example value of this variable first:

     ;; Messages from the mailer daemon are not crossposted to any of
     ;; the ordinary groups.  Warnings are put in a separate group
     ;; from real errors.
     (| ("from" mail (| ("subject" "warn.*" "mail.warning")
        ;; Non-error messages are crossposted to all relevant
        ;; groups, but we don't crosspost between the group for the
        ;; (ding) list and the group for other (ding) related mail.
        (& (| (any "ding@ifi\\.uio\\.no" "ding.list")
              ("subject" "ding" "ding.misc"))
           ;; Other mailing lists...
           (any "procmail@informatik\\.rwth-aachen\\.de" "procmail.list")
           (any "SmartList@informatik\\.rwth-aachen\\.de" "SmartList.list")
           ;; Both lists below have the same suffix, so prevent
           ;; cross-posting to mkpkg.list of messages posted only to
           ;; the bugs- list, but allow cross-posting when the
           ;; message was really cross-posted.
           (any "bugs-mypackage@somewhere" "mypkg.bugs")
           (any "mypackage@somewhere" - "bugs-mypackage" "mypkg.list")
           ;; People...
           (any "larsi@ifi\\.uio\\.no" "people.Lars_Magne_Ingebrigtsen"))
        ;; Unmatched mail goes to the catch all group.

This variable has the format of a split. A split is a (possibly) recursive structure where each split may contain other splits. Here are the possible split syntaxes:

If the split is a string, that will be taken as a group name. Normal regexp match expansion will be done. See below for examples.
(field value [- restrict [...] ] split [invert-partial])
The split can be a list containing at least three elements. If the first element field (a regexp matching a header) contains value (also a regexp) then store the message as specified by split.

If restrict (yet another regexp) matches some string after field and before the end of the matched value, the split is ignored. If none of the restrict clauses match, split is processed.

The last element invert-partial is optional. If it is non-nil, the match-partial-words behavior controlled by the variable nnmail-split-fancy-match-partial-words (see below) is be inverted. (New in Gnus 5.10.7)

(| split ...)
If the split is a list, and the first element is | (vertical bar), then process each split until one of them matches. A split is said to match if it will cause the mail message to be stored in one or more groups.
(& split ...)
If the split is a list, and the first element is &, then process all splits in the list.
If the split is the symbol junk, then don't save (i.e., delete) this message. Use with extreme caution.
(: function arg1 arg2 ...)
If the split is a list, and the first element is ‘:’, then the second element will be called as a function with args given as arguments. The function should return a split.

For instance, the following function could be used to split based on the body of the messages:

          (defun split-on-body ()
                (goto-char (point-min))
                (when (re-search-forward "Some.*string" nil t)

The buffer is narrowed to the header of the message in question when function is run. That's why (widen) needs to be called after save-excursion and save-restriction in the example above. Also note that with the nnimap backend, message bodies will not be downloaded by default. You need to set nnimap-split-download-body to t to do that (see Client-Side IMAP Splitting).

(! func split)
If the split is a list, and the first element is !, then split will be processed, and func will be called as a function with the result of split as argument. func should return a split.
If the split is nil, it is ignored.

In these splits, field must match a complete field name.

Normally, value in these splits must match a complete word according to the fundamental mode syntax table. In other words, all value's will be implicitly surrounded by \<...\> markers, which are word delimiters. Therefore, if you use the following split, for example,

     (any "joe" "joemail")

messages sent from ‘’ will normally not be filed in ‘joemail’. If you want to alter this behavior, you can use any of the following three ways:

  1. You can set the nnmail-split-fancy-match-partial-words variable to non-nil in order to ignore word boundaries and instead the match becomes more like a grep. This variable controls whether partial words are matched during fancy splitting. The default value is nil.

    Note that it influences all value's in your split rules.

  2. value beginning with .* ignores word boundaries in front of a word. Similarly, if value ends with .*, word boundaries in the rear of a word will be ignored. For example, the value "@example\\.com" does not match ‘’ but ".*@example\\.com" does.
  3. You can set the invert-partial flag in your split rules of the ‘(field value ...)’ types, aforementioned in this section. If the flag is set, word boundaries on both sides of a word are ignored even if nnmail-split-fancy-match-partial-words is nil. Contrarily, if the flag is set, word boundaries are not ignored even if nnmail-split-fancy-match-partial-words is non-nil. (New in Gnus 5.10.7)

field and value can also be Lisp symbols, in that case they are expanded as specified by the variable nnmail-split-abbrev-alist. This is an alist of cons cells, where the car of a cell contains the key, and the cdr contains the associated value. Predefined entries in nnmail-split-abbrev-alist include:

Matches the ‘From’, ‘Sender’ and ‘Resent-From’ fields.
Matches the ‘To’, ‘Cc’, ‘Apparently-To’, ‘Resent-To’ and ‘Resent-Cc’ fields.
Is the union of the from and to entries.

nnmail-split-fancy-syntax-table is the syntax table in effect when all this splitting is performed.

If you want to have Gnus create groups dynamically based on some information in the headers (i.e., do replace-match-like substitutions in the group names), you can say things like:

     (any "debian-\\b\\(\\w+\\)" "mail.debian.\\1")

In this example, messages sent to ‘’ will be filed in ‘’.

If the string contains the element ‘\&’, then the previously matched string will be substituted. Similarly, the elements ‘\\1’ up to ‘\\9’ will be substituted with the text matched by the groupings 1 through 9.

Where nnmail-split-lowercase-expanded controls whether the lowercase of the matched string should be used for the substitution. Setting it as non-nil is useful to avoid the creation of multiple groups when users send to an address using different case (i.e., mailing-list@domain vs Mailing-List@Domain). The default value is t.

nnmail-split-fancy-with-parent is a function which allows you to split followups into the same groups their parents are in. Sometimes you can't make splitting rules for all your mail. For example, your boss might send you personal mail regarding different projects you are working on, and as you can't tell your boss to put a distinguishing string into the subject line, you have to resort to manually moving the messages into the right group. With this function, you only have to do it once per thread.

To use this feature, you have to set nnmail-treat-duplicates and nnmail-cache-accepted-message-ids to a non-nil value. And then you can include nnmail-split-fancy-with-parent using the colon feature, like so:

     (setq nnmail-treat-duplicates 'warn     ; or delete
           nnmail-cache-accepted-message-ids t
           '(| (: nnmail-split-fancy-with-parent)
               ;; other splits go here

This feature works as follows: when nnmail-treat-duplicates is non-nil, Gnus records the message id of every message it sees in the file specified by the variable nnmail-message-id-cache-file, together with the group it is in (the group is omitted for non-mail messages). When mail splitting is invoked, the function nnmail-split-fancy-with-parent then looks at the References (and In-Reply-To) header of each message to split and searches the file specified by nnmail-message-id-cache-file for the message ids. When it has found a parent, it returns the corresponding group name unless the group name matches the regexp nnmail-split-fancy-with-parent-ignore-groups. It is recommended that you set nnmail-message-id-cache-length to a somewhat higher number than the default so that the message ids are still in the cache. (A value of 5000 appears to create a file some 300 kBytes in size.) When nnmail-cache-accepted-message-ids is non-nil, Gnus also records the message ids of moved articles, so that the followup messages goes into the new group.

Also see the variable nnmail-cache-ignore-groups if you don't want certain groups to be recorded in the cache. For example, if all outgoing messages are written to an “outgoing” group, you could set nnmail-cache-ignore-groups to match that group name. Otherwise, answers to all your messages would end up in the “outgoing” group.