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?

2004-07-27: scmail 1.3 Released!
- Multiple occurrences of fields having the same name are now supported (ex. Delivered-To:).
- Other small modifications have been also made.
2004-03-11: scmail 1.2 Released!
- New option --dry-run (-n) for scmail-refile/scmail-deliver is added. (it works just like make -n)
- Short command line options are now supported.
2004-02-05: scmail 1.0 Released!
- A spam filter called scbayes is now included
  - scbayes is developed by Shiro Kawai.
- Names of configuration files are changed. You can keep using old names but I recomend you to rename them.
  - ~/.scmailrc -> ~/.scmail/config
  - ~/.scmailrc-deliver -> ~/.scmail/deliver-rules
  - ~/.scmailrc-refile -> ~/.scmail/refile-rules
  - ~/.scmail-log -> ~/.scmail/log
- Writing a rule using lambda becomes easy.
  - Please see a sample code in dot.scmail/deliver-rules.sample.
- Many codes are rearranged.
- A test suite is prepared (make check)
2002-10-24: scmail 0.1 Released!

Requirements

Gauche 0.7.4.1 or later

Characteristics

Written simply in Scheme.
spam filter scbayes is included. (now testing)
scmail supports MH and Maildir mailboxes.
Simple filtering rules can be written in S-expressions.
Advanced filtering rules can be written in Scheme programs.
scmail can filter an incoming mail when it is received (like procmail).
scmail can filter mails in a mailbox.

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

scmail-deliver: a command to filter an incoming mail when it is received.
scmail-refile: a command to filter mails in a mailbox.
scbayes: a command to learn spam and nonspam mails for spam filtering.

Configuration

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

#{../dot.scmail/config.sample}

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

#{../dot.scmail/deliver-rules.sample}

dot.scmail/refile-rules.sample

#{../dot.scmail/refile-rules.sample}

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

Simon Cozens: Filtering Mail with Mail::Audit and News::Gateway, The Perl Journal, Vol. 5, No. 2. (2000)
- Describing a mail filter written in Perl. It starts with a strong message: "Let's face it. procmail is horrid."