called in a buffer narrowed to the message in question. The function
receives one argument, the name of the group the message comes from.
The return value should be `delete' or a group name (a string)."
+ :version "21.1"
:group 'nnmail-expire
:type '(choice (const delete)
(function :format "%v" nnmail-)
(defcustom nnmail-scan-directory-mail-source-once nil
"*If non-nil, scan all incoming procmail sorted mails once.
It scans low-level sorted spools even when not required."
+ :version "21.1"
:group 'nnmail-procmail
:type 'boolean)
(defcustom nnmail-extra-headers nil
"*Extra headers to parse."
+ :version "21.1"
:group 'nnmail
:type '(repeat symbol))
(defcustom nnmail-split-header-length-limit 512
"Header lines longer than this limit are excluded from the split function."
+ :version "21.1"
:group 'nnmail
:type 'integer)