Filtering Mail

In our system, the traditional ~/.forward file is used only to catch mail from unconfigured Linux machines and so is set to forward mail to the mail server. Inbound mail at the server is eventually disposed of according to instructions in .exim files which you can use to forward or filter message.

Before processing .exim the origin of a message is checked against blacklists and whitelists of senders and the content of a message may cause it to be marked as spam. You can choose how much of this preprocessing you want and you can use the .exim files to specify your own filtering.

Note:.exim files live in the home directory on the mailserver not your normal home directory so you must create/copy them to gpo.stanford.edu.

Simple .exim file for forwarding

To forward your mail elsewhere put the e-mail address in the ~/.exim just as you would in a traditional ~/.forward file,e.g:

descartes@academie.fr

Introduction to .exim file syntax

Each line in a non-empty .exim file provides a comma-separated list of delivery instructions beginning with one of #,/,|, or text interpreted as follows::

# - comment
Lines beginning with "#" are normally not processed. However if the first line of a .exim file is:
# Exim filter
then the .exim file is taken to be an filter as described in the exim filter specification.
| - piped command
Lines beginning with "|" are pipelines which are run in a shell (/bin/sh).
- To use procmail create both a .procmailrc file and a .exim consisting of:
  | procmail -f -
  This sample-procmailrc files marked spam unless it contains conference annoucments
  To use maildrop. create both a .mailfilter file and a .exim consisting of:
  |maildrop
  This sample-mailfilter discards high-scoring spam while filing the rest.
/ - local file
Lines beginning with a "/" designate local files in either traditional mbox (if the line does not end in "/") or qmail's maildir format (if the line does end in "/"). The maildir can be a useful format but is not supported by our imap server.
forwarding address
All other lines are processed as a comma-separated lists of e-mail address.
They must by fully-qualified names and not contain any spaces, e.g. descartes@graphics.stanford.edu not descartes@graphics

Spamassassin

To opt-out of Spamassassin processing at graphics, simply remove the ~/.spamassassin directory on gpo.

Spamasssassin works by scanning the headers and body of messages looking for suspect content. Each test generates a score value and when the score exceeds a user-definable threshhold, the mail declared to be spam. The original message is then made an attachment to a SPAM report.

To customize Spamaassin scoring and reporting for your mail, you can add lines to the defaults in:

~/.spamassassin/user_prefs to alter your Spamassassin User Preferences

Mail which comes via an @cs.stanford.edu address is normally run through the global Spamassassin on the CS servers and not filtered a second time at graphics. You can customize some of the CS settings at: CS Spamasassin Settings

If you want your graphics preferences to be used instead, you can ask to be added to theCS Spamassassin opt-out list by sending a request to action@cs.stanford.edu.

Sample filter files

The links below point at two simple examples of personal mailfilter files that work with the headers added by SpamAssassin.

Maildrop sample-mailfilter
Discard high-scoring spam while filing the rest
Procmail sample-procmailrc
File marked spam unless it contains conference annoucments