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Automatic list creation

Note

  • Situation: you want to create lists according to specified criteria (age, geographical location, etc.).
  • Problem: Creating all the possible lists would result in thousands of list creation, many of them (but you don't know which one...) would never be used.

Automatic list creation allows you to define those potential lists through family parameters, but they will not be created at once. The mailing list creation is triggered when Sympa receives a message addressed to this list.

To enable automatic list creation, you will have to:

Configuring your MTA

The familyqueue solution (with postfix)

To do so, you have to configure your MTA for it to add a custom header field to messages. The easiest way is to customize your aliases manager, so that mails for automatic lists are not delivered to the normal queue program, but to the familyqueue dedicated one. For example, you can decide that the name of those lists will start with the auto- pattern, so you can process them separately from other lists you are hosting.

familyqueue expects 2 arguments: the list name and family name (whereas the queue program only expects the list address).

Now let's start with a use case: we need to communicate to groups of co-workers, depending on their age and their occupation. We decide that, for example, if we need to write to all CTOs who are fifty years old, we will use the auto-cto.50@lists.domain.com mailing list. The occupation and age informations are stored in our LDAP directory (but of course we could use any Sympa data source: SQL, files...). We will create the age-occupation family.

First of all we configure our MTA to deliver mail to 'auto-*' to familyqueue for the age-occupation family. We'll also need to tell the MTA to accept mail for addresses that do not yet exist since by default postfix will reject mail for unknown local users.

/etc/postfix/main.cf

...
transport_maps = regexp:/etc/postfix/transport_regexp
local_recipient_maps = pcre:/etc/postfix/local_recipient_regexp unix:passwd.byname $alias_maps
sympa_destination_recipient_limit = 1
sympabounce_destination_recipient_limit = 1
sympafamily_destination_recipient_limit = 1

/etc/postfix/transport_regexp

/^.*-owner\@lists\.domain\.com$/      sympabounce:
/^auto-.*\@lists\.domain\.com$/       sympafamily:
/^.*\@lists\.domain\.com$/            sympa:

/etc/postfix/local_recipient_regexp

/^.*-owner\@lists\.domain\.com$/  1
/^auto-.*\@lists\.domain\.com$/   1

/etc/postfix/master.cf (Note: Replace $LIBEXECDIR below)

sympa     unix  -       n       n       -       -       pipe
  flags=hqRu null_sender= user=sympa argv=$LIBEXECDIR/queue ${recipient}
sympabounce  unix  -       n       n       -       -       pipe
  flags=hqRu null_sender= user=sympa argv=$LIBEXECDIR/bouncequeue ${recipient}
sympafamily  unix  -       n       n       -       -       pipe
  flags=hqRu null_sender= user=sympa argv=$LIBEXECDIR/familyqueue ${recipient} age-occupation

A mail sent to auto-cto.50@lists.domain.com will be queued to the $SPOOLDIR/automatic spool, defined by the queueautomatic sympa.conf parameter (see queueautomatic). The mail will first be processed by an instance of the sympa.pl process dedicated to automatic list creation, then the mail will be sent to the newly created mailing list.

The sympa-milter solution (with Postfix or Sendmail)

If you don't use postfix or don't want to dig in postfix alias management, you have an alternative solution for automatic listes management: sympa-milter.

This program is a contribution by Jose-Marcio Martins da Cruz.

What it does is checking all incoming mails and, if it recognizes a message to an automatic list, adds the relevant headers in it and places it in Sympa's automatic spool. It replaces familyqueue.

Sympa-milter will work with Sendmail 8 or Postfix built with milter support.

Note

  • As of Sympa 6.2, sympa-milter 0.7 or better is required and file_prefix configuration should be added. If you were using earlier versions, please consider upgrading.

This is the procedure to make it work:

Install sympa-milter

You can download the latest version from the download site.

Once you have the archive, decompress it: tar xzvf sympa-milter-0.7.tgz.

You will need the libmilter library to build the sympa milter. This can be found in the development files of sendmail. You can install it, for example on a RedHat system, with the following command:

yum install sendmail-devel

Then install the program:

# cd sympa-milter-0.7/
# ./configure
# make
# make install

The default install directory is /usr/local/sympa-milter/ (you can change this value with the --prefix configure option).

The install process also adds a launcher into /etc/init.d/, named sympa-milter. You'll need to setup links to it under /etc/rc3.d. If you're using Fedora like Linux distributions, you can use /sbin/chkconfig to setup these links.

/sbin/chkconfig sympa-milter on

You must then set up the configuration file, sympa-milter.conf. You will find a sample configuration file inside /usr/local/sympa-milter/etc directory. This file contains two sections whose border are XML-like tags. Inside a section, a parameter is defined on a single line by the sequence:

parameters_name            parameter_value

family        recipient_regular_expression

You should use "plussed aliases" (at least with sendmail) to identify user existence more easily.

Here is an example of sympa-milter.conf, filled-up with default values :

#
# Section general
#
<general>
log_level        10
log_facility            local6
log_severity            yes

socket                  inet:2030@localhost

spool_dir               /usr/local/sympa-milter/var

pid_file                /usr/local/sympa-milter/var/sympa-milter.pid

run_as_user             sympa
run_as_group            sympa

file_prefix             list
</general>
#
# Section families
#
<families>
# Syntax :
#     family        recipient regular expression
#
joe                  ^joe+.*@one.domain.com
toto                 ^bob+toto@other.domain.com
best                 ^best.*@another.domain.com
</families>

Note:

You can use any regular expression to define the addresses used by your family.

Set up your MTA

What you must do to make all the thingy to work is:

auto    : /dev/null

or

auto    : "some_file"

Reload your MTA config. All set!

Defining the list family

We need to create the appropriate etc/families/age-occupation/config.tt2. All the magic comes from the TT2 language capabilities. We define on-the-fly the LDAP source, thanks to TT2 macros.

$SYSCONFDIR/families/age-occupation/config.tt2

...
user_data_source include2

[%
occupations = {
    cto = { title=>"chief technical officer", abbr=>"CHIEF TECH OFF" },
    coo = { title=>"chief operating officer", abbr=>"CHIEF OPER OFF" },
    cio = { title=>"chief information officer", abbr=>"CHIEF INFO OFF" },
}
nemes = listname.split('-');
THROW autofamily "SYNTAX ERROR: listname must begin with 'auto-' " IF (nemes.size != 2 || nemes.0 != 'auto');
tokens = nemes.1.split('\.');
THROW autofamily "SYNTAX ERROR: wrong listname syntax" IF (tokens.size != 2 || ! occupations.${tokens.0} || tokens.1 < 20 || tokens.1 > 99 );
age = tokens.1 div 10;
%]

custom_subject [[% occupations.${tokens.0}.abbr %] OF [% tokens.1 %]]

subject Every [% tokens.1 %] years old [% occupations.${tokens.0}.title %]

include_ldap_query
attrs mail
filter (&(objectClass=inetOrgPerson)(employeeType=[% occupations.${tokens.0}.abbr %])(personAge=[% age %]*))
name ldap
port 389
host ldap.domain.com
passwd ldap_passwd
suffix dc=domain,dc=com
timeout 30
user cn=root,dc=domain,dc=com
scope sub
select all

The main variable you get is the name of the current mailing list via the listname variable as used in the example above.

Configuring Sympa

Now we need to enable automatic list creation in Sympa. To do so, we have to:

You can make Sympa delete automatic lists that were created with zero list members; to do so, you should set the automatic_list_removal parameter to if_empty.

sympa.conf

...
automatic_list_feature  on
automatic_list_creation public
automatic_list_removal  if_empty

While writing your own automatic_list_creation scenarios, be aware that:

Now you can send message to auto-cio.40 or auto-cto.50, and the lists will be created on the fly.

You will receive an 'unknown list' error if either the syntax is incorrect or the number of subscriber is zero.

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