This document provides an overview and tutorial of Dbmail, an open source email system that stores and retrieves email messages from a database like MySQL or PostgreSQL for improved scalability, manageability, speed, and security compared to traditional filesystem-based email systems. It describes how Dbmail works by integrating with MTAs like Sendmail or Postfix to deliver emails to the database, and uses POP3 and IMAP daemons to retrieve emails from the database for users. Configuration files and sample postfix configurations are also shown.

1. La nueva generación
de correo electrónico
Tutorial para el Congreso
Internacional de Software Libre GULEV
Noviembre 25 de 2004
Derechos reservados © 2004 Sandino Araico Sánchez
<sandino@sandino.net>
Se permite ilimitadamente el uso, copia, redistribución con o sin
modificaciones siempre y cuando se mantenga el aviso de
derecho de autor y se anoten al final de la presentación todas las
modificaciones que se llevan a cabo conservando la historia de
las modificaciones que hagan las demás personas e indicando la
fecha de cada modificación y el nombre de la persona que la
llevó a cabo.

2. Overview
Dbmail is the name of a group of programs that
enable the possiblilty of storing and retrieving
mail messages from a database. Currently
MySQL and PostgreSQL can be used as database
backends. Development and support of dbmail is
done by IC&S, a Dutch company specialized in
Linux development and support. The dbmail
developers can be reached through the dbmail
mailinglist.

3. What are the advantages?
Scalability
Dbmail is as scalable as the database system
that is used for the mail storage. In theory
millions of accounts can be managed using
dbmail. One could, for example, run 4
different servers with the pop3 daemon each
connecting to the same database (cluster)
server.

4. What are the advantages?
Manageability
Dbmail is based upon a database. Dbmail can
be managed by changing settings in the
database (f.e. using PHP/Perl/SQL), without
needing shell access.

5. What are the advantages?
Speed
Dbmail uses very efficient, database specific
queries for retrieving mail information. This is
much faster then parsing a filesystem.

6. What are the advantages?
Security
Dbmail has got nothing to do with the
filesystem or interaction with other programs
in the Unix environment which need special
permissions. Dbmail is as secure as the
database it's based upon.

7. What are the advantages?
Flexibility.
Changes on a Dbmail system (adding of users,
changing passwords etc.) are effective
immediately.

8. How Dbmail works
A normal MTA
sendmail dbmail-smtp
qmail dbmail-lmtp
postfix
MySQL
Incoming mail Postgres

9. How Dbmail works
dbmail-pop3d
dbmail-imapd
MySQL
User retreiving email Postgres

10. What’s inside the DB?
aliases message blocks
users
mailboxes messages

11. dbmail.conf
[DBMAIL]
# Database settings
host=localhost
user=dbmail
pass=********
db=dbmail
# trace level for dbmail-maintenance
TRACE_LEVEL=2

12. dbmail.conf
[SMTP]
SENDMAIL=/usr/sbin/sendmail
# your sendmail executable, this is needed for
boucing mail
DBMAIL_FROM_ADDRESS=dbmail-bounce@sandino.net
# the email address where bounces come from
POSTMASTER=dbmail@sandino.net
# postmaster's email address (which is used in
the bounce messages)
AUTO_NOTIFY=no
AUTO_REPLY=yes
TRACE_LEVEL=1

13. dbmail.conf
[POP]
EFFECTIVE_USER=dbmail
EFFECTIVE_GROUP=dbmail
#BINDIP=69.93.121.178
BINDIP=*
PORT=110
NCHILDREN=50
MAXCHILDREN=200
MAXCONNECTS=10000
TIMEOUT=300
RESOLVE_IP=yes
POP_BEFORE_SMTP=yes
TRACE_LEVEL=1

14. dbmail.conf
[IMAP]
EFFECTIVE_USER=dbmail
EFFECTIVE_GROUP=dbmail
#BINDIP=69.93.121.178
BINDIP=*
PORT=143
NCHILDREN=15
MAXCONNECTS=10000
#TIMEOUT=3600
TIMEOUT=300
RESOLVE_IP=yes
IMAP_BEFORE_SMTP=yes
TRACE_LEVEL=1

15. postfix transport
alpos.org dbmail:
apesta.org dbmail:
araico.net dbmail:
batracio.org dbmail:
delbebe.com.mx dbmail:
correo.delbebe.com.mx dbmail:
elmundo.delbebe.com.mx dbmail:
delbordado.com dbmail:
correo.delbordado.com dbmail:
elmundo.delbordado.com dbmail:
h-o-p-p.org dbmail:
royald.net dbmail:
royald.org dbmail:
sandino.net dbmail:
tumamafuemia.com dbmail:

16. postfix master.cf
dbmail unix - n n - - pipe
flags= user=dbmail:dbmail argv=/usr/bin/dbmail-smtp -d
${recipient}

17. postfix main.cf
local_recipient_maps = pgsql:/etc/postfix/users.cf
relay_recipient_maps = pgsql:/etc/postfix/users.cf
mynetworks = 69.93.121.178/32, pgsql:/etc/postfix/my_net.cf

18. postfix users.cf
users.cf:
user = dbmail
password = ********
dbname = dbmail
table = aliases
hosts = localhost
select_field = alias_idnr
where_field = alias

19. postfix my_net.cf
my_net.cf:
user = dbmail
password = ********
dbname = dbmail
table = pbsp
hosts = localhost
select_field = since
where_field = ipnumber
additional_conditions = and since > (now() - interval '1 hour')

20. Referencias
http://dbmail.org
http://dbmail.org/dokuwiki/doku.php

21. Gracias
<sandino@sandino.net>