scmail: a mail filter written in Scheme

Last Modified: 2004-07-27 (Since: 2002-10-24)

What's scmail?

scmail is a mail filter written in Scheme. scmail can filter an incoming mail when it is received and filter mails in a mailbox. A bayesian spam filter called scbayes is also included.

What's new?

Requirements

Characteristics

Installation

To install scmail, run the following commands.

% gzip -dc scmail-1.3.tar.gz | tar xvf - 
% cd scmail-1.3
Password: (enter root's password)
# make
# make install

Components

Configuration

Copy a sample file (~/dot.scmail/config.sample) to ~/.scmail/config and edit it.

;; -*- scheme -*-
(
 :smtp-host "localhost"
 :log-file  "~/.scmail/log"
 :umask     #o077

 ;; for usual mail filtering
 :refile-rules  "~/.scmail/refile-rules"
 :deliver-rules "~/.scmail/deliver-rules"

 ;; for spam filtering
 :token-table   "~/.scmail/token-table.dbm"
 :digest        "~/.scmail/digest.dbm"

 ;; for MH
 :mailbox   "~/Mail"
 :inbox     "inbox"
 :spam      "spam"   ; a folder for spam mails
 :mailbox-type  mh

 ;; for Maildir
 ;; :mailbox   "~/Maildir"
 ;; :inbox     ""
 ;; :spam      ".spam"   ; a folder for spam mails
 ;; :mailbox-type  maildir
 )

Using scmail-deliver

scmail-deliver is a command to filter an incoming mail when it is received. scmail-deliver uses Filtering rules defined in ~/.scmail/deliver-rules. You can copy a sample file (dot.scmail/deliver-rules.sample) to ~/.scmail/deliver-rules.

If your mail server is Sendmail or Postfix, you can put the following ~/.forward file to filter an incoming mail when it is received.

| /usr/local/bin/scmail-deliver

If you are using fetchmail to fetch mails from a POP server, you can add the following code into your ~/.fetchmailrc file to use scmailrc-deliver.

poll pop3.example.org
     protocol apop
     user satoru
     mda "/usr/local/bin/scmail-deliver"
     no mimedecode

Using scmail-refile

scmail-refile is a command to filter mails in a mailbox. scmail-refile uses Filtering rules defined in ~/.scmail/refile-rules. You can copy a sample file (dot.scmail/refile-rules.sample) to ~/.scmail/refile-rules.

To use scmail-refile, run it on the command line like the following:

% scmail-refile
refile: inbox/93 -> ml/enkai@coboler/57
refile: inbox/94 -> ml/linux-zaurus/218
refile: inbox/98 -> ml/linux-zaurus/219
refile: inbox/99 -> ml/ming/42

In this example, the first line in the output messages shows a mail 93 in inbox folder is refiled to ml/enkai@colber as a mail 57. ~/.scmail/log file contains the same report with time information.

% tail -5 ~/.scmail/log
2002-09-26T12:49:31: refile: inbox/93 -> ml/enkai@coboler/57  
2002-09-26T12:49:31: refile: inbox/94 -> ml/linux-zaurus/218  
2002-09-26T12:49:31: refile: inbox/98 -> ml/linux-zaurus/219
2002-09-26T12:49:31: refile: inbox/99 -> ml/ming/42

Filtering rules

You can edit sample files.

dot.scmail/deliver-rules.sample

;; -*- scheme -*-

;;
;; Copy all mails to "inbox-all" folder for backup.
;;
(add-filter-rule!
 (lambda (mail) (copy mail "inbox-all")))

(add-filter-rule!
 ;;
 ;; Forward a mail from "partner@example.net" to "mobile@example.com".
 ;; (a copy of mail remains)
 ;;
 '(from
   ("partner@example.net" (forward "mobile@example.com")))

 ;;
 ;; Redirect a mail from "partner@example.net" to "mobile@example.com".
 ;; (a copy of mail doesn't remain)
 ;;
 '(from
   ("partner@example.net" (redirect "mobile@example.com")))

 ;;
 ;; Drop a mail writtein in unreadable charcodes to "spam".
 ;; For people who cannot read a mail written in Chinese and Korean.
 ;;
 '(content-type
   (#/gb2312|euc-kr|big5|gbk|ks_c_5601/i
             "spam"))

 ;;
 ;; Drop a Japanese spam mail to "spam" folder.
 ;;
 '(subject
   ((#/[未末]承[認諾]広告[*＊※]/ #/[！!]広告[！!]/)
    "spam")))

;;
;; Drop a mail containing "viagra" in Subject: and "text/html" in the body
;; to "spam" folder.
;;
(add-filter-rule!
 (lambda (mail)
   (and (mail 'subject "viagra")
        (mail 'body "text/html")
        (refile mail "spam"))))

;; Filter spam mails.
;; Please use scbayes to learn spam and nonspam mails beforehand.
;; (add-bayesian-filter-rule!)

;; Filter spam mails using a white list.
;; (use srfi-1)
;; (use scmail.bayesian-filter)
;; (define white-list
;;   (list "friends@example.net"
;;         "family@example.net"))
;; (add-filter-rule!
;;   (lambda (mail)
;;     (and (not (any (cut mail 'from <>) white-list))
;;          (mail-is-spam? mail)
;;          (refile mail "spam"))))

dot.scmail/refile-rules.sample

;; -*- scheme -*-

(add-filter-rule!
 ;;
 ;; Refile a mail from "foo@example.jp" to "from/foo" folder.
 ;;
 '(from
   ("foo@example.jp" "from/foo"))

 ;;
 ;; Refile a mail to "admin@example.com" to "admin" folder.
 ;;
 '(to/cc
   ("admin@example.com" "admin"))

 ;;
 ;; Refile a mail from a mailing list according to List-Id header.
 ;; e.g. "List-Id: <ml.example.jp>" => "ml/ml.example.jp"
 ;;
 '(list-id
   (#/<([-.\w]+)>/  "ml/\\1"))

 ;;
 ;; Refile a mail from a mailing list according to X-ML-Name header.
 ;; e.g. "X-ML-Name: foo-ml" => "ml/foo-ml"
 ;;
 '(x-ml-name
   (#/([-.\w]+)/  "ml/\\1"))

 ;;
 ;; Refile a mail from satoru@example.jp or satoru@example.org
 ;; to "from/satoru" folder.
 ;;
 '(from
   (("satoru@example.jp" "satoru@example.org") "from/satoru")))

;; Replace unsafe characters with `-' in match data.
(set-match-data-replace-rule! '(#/[^a-zA-Z0-9_-]/ "-"))

;; Filter spam mails
;; (add-bayesian-filter-rule!)

Using a spam filter

Please see scbayes's documentation.

FAQ

How does scmail handle a huge mail?

Since scmail handles a mail on memory entirely, a huge mail which cannot fit in memory is not supported. So, scmail-deliver perhaps loses an incoming huge mail.

What happens if a rule file has syntax errors?

scmail uses rules read correctly and broken rules are ignored. Messages of syntax errors are reported in ~/.scmail/log.

Download

scmail is a free software with ABSOLUTELY NO WARRANTY under so called "BSD licence".

References

Links

Satoru Takabayashi