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Configuring procmail with The Dotfile Generator
In this article, I'll describe how to configure procmail using The Dotfile
Generator (TDG for short). This will include:
It might be a good idea to download the program. To do that, please go to
the home page of
TDG, to find the nearest mirror. You might also be interesting in
article I've written about TDG for Linux
- How to sort mails coming from different mailing list
- How to setup an auto reply filter, when you are on vacation
- How to change some part of a letter, i.e. remove the signature
- How to avoid that mail get lost!
To start TDG with the procmail module, type dotfile procmail. Now
a window should appear like in figure 1. As you can see, the module is split
up in three pages, the first two are very simple, so lets start with the page
called General Setup. This page can be seen in figure 2.
On this page there are four things, to configure:
- The directory to use as prefix for all file operations. This is just
for ease, since all file operations may be with full prefix.
- Your email address, will be used in preventing loop-backs.
- Configuration of log files. These are very
useful, when you wish to investigate where
the different mail went. If you turn on abstract logging, you
may find the program mailstat very useful. (See The log file below)
- The search path, in which procmail may find the programs which it
needs. Note this is only the programs, that you specify in filters etc.
Avoiding lost mail
Since procmail handles your incoming mail, the security is very important
to this module. This means that you may backup your incoming mail in three
different ways. To do this, go to the page called Backup. Part of
it can be seen in figure 3.
The first category of backup is to back up all incoming mail. The code, which
must be generated to the procmailrc file for this, will be written as the
very first line. This is to avoid that any errors in the generated procmail
file will throw away any of your mails. This sort of backup is only a
good idea when you at first start using the generated procmail file. The main
drawback is that all incoming mail is saved in one
file, and this file may become huge very fast.
The second method is to backup all incoming mail, which are delivered by
procmail. This may be a good idea to use, to verify that mail are
sorted into the right places.
The third method is to backup all mail, which makes it to your incoming
mailbox. This mail are often mails, which do not come from a mailing list,
and which are not junk mail to thrown away.
In the first method, you have to specify the full filename. This is because
this method has to be 100% full prof. In the next two methods you may build
the file names from the current date and time. This makes it
possible to save this sort of mail to folders, for the current
year/month/week etc. E.g. a folder called backup-delivered-1997-July
As an additional feature, you may keep the files as gziped files.
The backup of delivered mail may be specified for each individual recipe,
or for all recipes at once. (see figure 4 check box 9)
To learn how to use the FillOut elements, which configures the file to save
to, please see the
Dotfile Generator article in Linux Journal.
Setting up the recipes
In procmail a central concept is a recipe. A recipe is a set of
conditions, and a set of actions. All the actions are executed, if all of
the conditions is fulfilled. Below is a few examples of conditions:
A list of actions may include:
- The letter comes from firstname.lastname@example.org
- The subject is subscribe
- The size of the letter is greater than 1Mb
- The letter contain the text ...
A procmail configuration is a sequence of recipes. When a letter arrive,
each recipe is checked to see if all its conditions are fulfilled. If they
are, the actions of the recipe is executed.
- Reply to the sender, that you are on holiday
- forward the letter to another person
- save the letter to a file
- change some part of the letter (i.e. add a new header field, add some
text to it etc.)
Procmail will finish testing recipes when one is matched, unless a flag is
set to tell it, that this recipe should not stop the deliverment (see
figure 4 check box 8). This means that the order of the recipes are
important, since only the first recipe, which match will process the letter.
If none of the recipes are fulfilled, or if the ones which are fulfills
have check box 8 in figure 4 set, the letter is delivered to the incoming
mailbox as if the procmail filter haven't been there at all.
You configure the recipes on the page called ``Recipes''. This page can be
seen in figure 4.
What you see here is an ExtEntry. An ExtEntry is a widget, which repeats it
elements as many times as necessary (just like a list box repeats the
labels.) All what you see on this page, is one single recipe. To see a new
recipe, you have to scroll the outer scroll bar (1). To add a new
recipe, you have to press the button below the scroll bar.
As described above, a recipe is a set of conditions. This set is also
represented with an ExtEntry (2). To scroll to another condition in a
recipe, you have to use scroll bar (2), and to add a new condition, you have to
use the button below scroll bar (2).
You may give each recipe a unique name, which will make it easier to find a
given recipe. This name will also be written to the file with mail delivered by recipes (method 2 above), so you can
see which recipe matched the actual letter. To give a recipe a name, use
entry (3). At the right side of the entry, a button labeled Idx is
located. This is a quick index to the outer ExtEntry (i.e. the recipes). If
you press this button a list box will drop down, where you may select one
of the recipes to scroll to, by its name.
The conditions of a recipe
The most common condition one wishes to set up, is that one of the header
fields matches a given regular expression, or that the body of the letter
matches a given regular expression. To explain how to do that, lets first
see what a header may look like.
From procmail-request@Informatik.RWTH-Aachen.DE Tue Jan 28 16:30:46 1997
Date: Tue, 28 Jan 1997 10:06:28 -0500 (EST)
From: Rick Troxel <email@example.com>
Subject: Re: Lynx as an external viewer for pine
To: procmail mailing list <procmail@Informatik.RWTH-Aachen.DE>
Cc: "Robin S. Socha" <firstname.lastname@example.org>
The very first line of the letter is special. This line has been
written by the program sending the letter (often called sendmail). This
header field is often always the same for a given mailing list, so to sort
mail from a mailing list, it might be a good idea to read the letter with an
ordinary file reader (NOT a mail reader, as it will seldom show this
line). And copy this information to the pattern field (figure 4, label
(6) ). As the element to match, you have to select Sendmail from
in entry (5).
Three special macros exists in procmail. These may be used, when matching
To see what these macros stand for, please refer to the manual page called
- This macro matches every destination specifications.
- This should match when the letter comes from a daemon (which
includes mailing lists). This is useful, to avoid creating a mail
loop with some mailing list.
- An other regular expression, which matches that the letter comes
from mail daemon.
There is a lot of header fields to chose between in the pull down menu
(5), but if the one you wish to select isn't located there, you may type it
The check box (4) may be used to negate the condition, i.e. the pattern
shall not match to fulfill the condition.
So far, I have mentioned that you may type a regular expression in (6). In
most cases, it may not be necessary to know anything about regular
expressions, since the procmail module will take care of most of it for
you. One thing may be worth to know anyway, and that is that you may match
``anything'' with .* This means that abc.*def will match
anything which start with abc and ends with def, eg. abcdef or
abcXXXXdef. To see a more detailed description of the set of regular
expression, that procmail uses, you may press the button labeled
One common pitfall is to forget to match everything at the start of the
line. I.E. If you wish to set up a regular expression for the From:
field above, it is not enough to give the pattern:
email@example.com, since this is not at the start of the line,
you have to tell procmail that every mail messages, which includes the text
firstname.lastname@example.org is to be handled, I.E. insert .* in
front of the email address.
Letting an external program decide whether a condition is
A final way to set up a condition is by using an external program to verify
some conditions. This is done by pressing button (7). This will bring up a
window with a FillOut like the one you can see in figure 3. This time,
however, the entry has been replaced with a text box. In this text box you
may type some commands, which reads either the header or the body on
standard input. These command may refer to some header fields from the
letter. The line (separated with a newline) will be joined together with a
separating semicolon. This makes each line a separate command.
Procmail will consider the condition fulfilled if the exit code from the
program is 0 and not otherwise. This behavior may be changed with the
check button (4) in figure 4.
The actions, that this module can handle is split up in six parts. These
are described in detail below. To activate an action, you first have to
select the check box, which is located next to it. This is, to make it clear
which actions are enabled for a given recipe.
In the window which appear, when you press the button
labeled Predesigned Filters, you may set up a filter. This filter
may change the header fields, add new header fields and/or remove existing
On this page you will find one custom-made filter: Remove
signatures. With this filter, you may specify a signature for each
email address. If the text you specify is found (exactly!) it will be
removed from the letter. My intention is that more custom-made filters will
be added, as users send me their ideas and filters.
If you wish to create your own filter, you have to go the page Handmade
filters. On this page, you may send the header and/or the body of a
letter through a command.
As an example, you may remove the header with the command cat - >>
/dev/null, or add a message to the body of a message with the command
echo This letter has been resent to you, by my procmail filter!; cat -
If only the filter actions is selected, the
filter will change the letter permanently, i.e. the changes will have effect
on the subsequent recipes (even on the delivered letter, if no recipe
match!) This may be useful if you e.g. uses a mail reader, which does not
support mime, and you have a filter, which can convert mime encoded text to
7 bit ascii.
If however one of the other actions are enabled, the changes will only have
effect within this recipe!
The reply action
With the reply action, you may set up a reply mechanism, which sends a
letter back to the sender, with a message you specify. One feature of this
mechanism is that you may specify how often a reply should be send, you
have the following possibilities.
This is useful, if you leave on vacation, and wish to send a message that
you will not read your letter at once.
- Send a reply to each letter
- Send a reply only once
- Send only a reply if it is more than a given number of days since
the last reply was send.
The reply is only sent, if the letter does not come from a daemon, to avoid
that you sent a reply to every message on a mailing list.
The forward action
With the forward action, you may forward letters to other email
The save to file action
With this action, you may save the letter to a file. The file name is
specified with a FillOut widget, just like you specified the name of a file
to save backups to. This time, however, you have two additional features:
you may use the content of a header field, or you may use the output from a
command. In figure 5, you can see how to select a header field to extract
as part of the file name.
Email addresses may be given in three ways:
If you select that the field is an email address, you may specify that you
wish to extract the user name with or without the domain part.
- real name <email>
- email (real name)
Finally, you may pipe the header field though a command you specify
yourself. This command may read the value of the header field on standard
input, and write to standard output.
The pipe action
With the pipe action, you may specify a command, which takes care of the
letter. This command may read the letter on standard input, and may not write
anything (it will be ignored!).
The procmail file generated from TDG, contain lots of
comments, which should make it easy for you to find a specific recipe, in
case you wish to see what it look like.
Should something go wrong, you may turn on extended diagnostic, this will
write additional lines to the log file, which lets you see what it does. To
debug this, you have to read both the log file and the procmail
If you use the log abstract options, you will find the program
mailstat very useful. This will tell you how many letters have been
delivered where. One line in the output from the mailstat programs is fake,
and that is the line, which says: /bin/false. This
line is due to the way that the generated code look. When you wish to throw
away a letter, in a way so you can explicit see that is has been dumped,
you should deliver it to the file called /dev/null. Please note
that you can only use the mailstat program, if extended diagnostic is
Before procmail start filtering all your incoming mail, you have to add
the following line to the file called ~/.forward:
"|IFS=' ' &&exec /usr/local/bin/procmail -f-||exit 75 #YOUR_USERNAME"
With the correct pathname for procmail, and your email address replaced
Here's a few link, which you may find interesting:
- The procmail mailing list
- To subscribe to the procmail mailing list, send a letter to email@example.com. Letters to it should be send to firstname.lastname@example.org
- Procmail Mini-Tutorial in Linux Gazette
- In The Linux Gazette issue 14, Jim Dennis has written a mini howto
- Procmail Mini-FAQ
- Era Eriksson Has created an excellent FAQ for procmail, which may be worth visiting before you ask anything on the mailing list
- The home page of
the Dotfile Generator
- At the home page of The Dotfile Generator, you may find additional
information about the other modules, which TDG contains (at the
moment this include: Bash, Elm, Emacs, ipfwadm, Fvwm1, Fvwm2, Tcsh
Copyright © 1997, Jesper Pedersen
Published in Issue 23 of the Linux Gazette, December 1997