How To Set Up a Postfix Email Server with Dovecot: Dynamic Maildirs and LMTP

Published on December 17, 2013

Lukas Erlacher

How To Set Up a Postfix Email Server with Dovecot: Dynamic Maildirs and LMTP


This tutorial is based on How To Set Up a Postfix E-Mail Server with Dovecot and picks up where the first part ended.

Please go through that tutorial first.

In this article, we will divorce mailboxes from system accounts using dovecot’s LMTP server as delivery mechanism, as well as use postgresql to keep user records.

No more mail will be delivered to the standard linux mailboxes.

Like the first guide, this tutorial is based on Debian 7 wheezy, Postfix 2.9, and dovecot 2.1 (+ Postgresql 9.1).


Install postgresql:

# aptitude install postgresql postfix-pgsql

dovecot in version 2.1 should already come with pgsql enabled. If you’re on a system where dovecot is modularised, run

# aptitude install dovecot-lmtpd dovecot-pgsql

to install the needed modules.

Postgres Database Setup

Adjust this for your needs if you already have a postgres setup running! But from a fresh postgres install, let’s set up authentication so that we can give dovecot access to the database. Add the following to /etc/postgresql/9.1/main/pg_ident.conf:

mailmap         dovecot                 mailreader
mailmap         postfix                 mailreader
mailmap         root                    mailreader

And the following to /etc/postgresql/9.1/main/pg_hba.conf (Warning: Make sure to add it right after the Put your actual configuration here comment block! Otherwise one of the default entries might catch first and the databse authentication will fail. )

local       mail    all     peer map=mailmap

Then reload postgresql (service postgresql reload). Now set up the database:

# sudo -u postgres psql
postgres=# CREATE USER mailreader;
postgres=# GRANT CREATE ON SCHEMA public TO postgres;
postgres=# GRANT USAGE ON SCHEMA public TO postgres;
postgres=# CREATE DATABASE mail WITH OWNER mailreader;
postgres=# \q 
# sudo psql -U mailreader -d mail
postgres=# \c mail

mail=# CREATE TABLE aliases (
    alias text NOT NULL,
    email text NOT NULL
mail=# CREATE TABLE users (
    email text NOT NULL,
    password text NOT NULL,
    maildir text NOT NULL,
    created timestamp with time zone DEFAULT now()
mail=# ALTER TABLE aliases OWNER TO mailreader;
mail=# ALTER TABLE users OWNER TO mailreader;
mail=# \q

You can then add virtual mailboxes like this, starting from a rootshell:

# doveadm pw -s sha512 -r 100
Enter new password: ...
Retype new password: ...
# psql -U mailreader -d mail
mail=# INSERT INTO users (

Administration Interface (optional)

If you don’t want to use the command line interface to maintain the mail database, you can set up an administration interface. Let’s first add a database user that is only allowed to edit the mail databse. Go back to /etc/postgresql/9.1/main/pg_hba.conf and add this line just under the peer authentication line you added earlier:

host pgadmin          mail              md5

This will allow local socket connections on port 5432. (The default port for postgres)

Add the database user:

# sudo -u postgres psql
postgres=# CREATE USER pgadmin WITH PASSWORD 'new password';
postgres=# \q

Give the user the privileges to edit the mail database:

# sudo psql -U mailreader -d mail
mail=> GRANT SELECT, UPDATE, INSERT, DELETE ON aliases TO pgadmin;
mail=> \q

You can now use an administration interface like pgAdmin that is capable of using SSH tunneling to directly connect to the database, or you could set up something like phpPgAdmin.

Dovecot Setup

We need to connect dovecot to the database and set up the LMTP server. Set up a new user (dovecot will refuse to handle mail without a system user set up for it) and directory for maildirs first: (you could use /var/mail, but that traditionally uses the mbox format, while we’re going to be using the superior maildir format).

# adduser --system --no-create-home --uid 500 --group --disabled-password --disabled-login --gecos 'dovecot virtual mail user' vmail
# mkdir /home/mailboxes
# chown vmail:vmail /home/mailboxes
# chmod 700 /home/mailboxes

Now save the following configuration as /etc/dovecot/dovecot-sql.conf:

driver = pgsql
connect = host=/var/run/postgresql/ dbname=mail user=mailreader
default_pass_scheme = SHA512
password_query = SELECT email as user, password FROM users WHERE email = '%u'
user_query = SELECT email as user, 'maildir:/home/mailboxes/maildir/'||maildir as mail, '/home/mailboxes/home/'||maildir as home, 500 as uid, 500 as gid FROM users WHERE email = '%u'

Make sure it is owned by root and chmodded 600.

Now open /etc/dovecot/dovecot.conf and edit the passdb and userdb settings to look like this:

userdb {
  driver = prefetch
passdb {
  args = /etc/dovecot/dovecot-sql.conf
  driver = sql

Change the protocols stanza to

protocols = imap lmtp

and add the lmtp service socket and some lmtp protocol settings:

service lmtp {
    unix_listener /var/spool/postfix/private/dovecot-lmtp {
    group = postfix
    mode = 0600
    user = postfix
protocol lmtp {

The mail_location stanza is now superfluous and can be removed.


We now need to tell postfix to deliver mail directly to dovecot. Open /etc/postfix/main.cf and add

mailbox_transport = lmtp:unix:private/dovecot-lmtp

to the end. Now we need to set the database config for postfix.

Create the file /etc/postfix/pgsql-aliases.cf and enter:


Then create the file /etc/postfix/pgsql-boxes.cf and enter:


Now amend the alias_maps line in main.cf to read

alias_maps = hash:/etc/aliases proxy:pgsql:/etc/postfix/pgsql-aliases.cf

and the local_recipient_maps line to read

local_recipient_maps = proxy:pgsql:/etc/postfix/pgsql-boxes.cf $alias_maps

In whole, your main.cf should look similar to this:

myhostname = mail.mydomain.com
myorigin = mydomain.com
mydestination = mydomain.com, mail.mydomain.com, localhost, localhost.localdomain
relayhost =
mynetworks = [::ffff:]/104 [::1]/128
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all

alias_maps = hash:/etc/aliases proxy:pgsql:/etc/postfix/pgsql-aliases.cf
local_recipient_maps = proxy:pgsql:/etc/postfix/pgsql-boxes.cf $alias_maps
mailbox_transport = lmtp:unix:private/dovecot-lmtp

smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
smtpd_tls_protocols = !SSLv2, !SSLv3

Finishing Up

Now simply reload:

# postfix reload

# service dovecot restart

And you’re set! Test your setup as you did after the first article, and make sure mail to postmaster@yourdomain.com finds its way into an attended mailbox!

Submitted by: Lukas Erlacher.

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Problem solved, changed dovecot.conf’s passdb and userdb entries to ones suggested in dovecot wiki: passdb { driver = sql args = /etc/dovecot/dovecot-sql.conf } userdb { driver = prefetch }

The userdb below is used only by lda.

userdb { driver = sql args = /etc/dovecot/dovecot-sql.conf }

Thanks for this great howto. Everything is working perfect, except sending an email to an alias.

If I create an entry in the aliases table, lets say email: mail1@domain.com (email exists in users table - receiving is working) alias: mail2@domain.com

When I send a mail to mail2@domain.com, I got the following SMTP error message: NOQUEUE: reject: RCPT from <ext-mailserver>: 550 5.1.1 mail2@domain.com: Recipient address rejected: User unknown in local recipient table;

Someone posted a solution, changing alias_maps to virtual_alias_maps, but this didn’t work for me.

I’d appreciate any help on that. Thanks a lot. ITD

Cool tutorial, but there’s one thing I had to change to get it to work. I had to change this:

userdb {
  driver = prefetch
passdb {
  args = /etc/dovecot/dovecot-sql.conf
  driver = sql

to this:

userdb {
  args = /etc/dovecot/dovecot-sql.conf
  driver = sql
passdb {
  args = /etc/dovecot/dovecot-sql.conf
  driver = sql
Kamal Nasser
DigitalOcean Employee
DigitalOcean Employee badge
January 16, 2014

@nandor: Glad you managed to get it working!

P.S.: <a href=“https://twitter.com/learlyman”>Lukas Erlacher</a> wrote this article, not me. :]

I am using dovecot authenticate to AD, so may I knwo where do I get this postmaster account?

As-is, this does not work on an Ubuntu 18.04 system.

What is missing here is that mydestination needs updated as well to include the domains you want to capture. In the event you capture multiple domains, you need to define it in mydestination.

I did a SQL database driven version of this in Postfix and Postgres to allow me to virtually define domains:

In /etc/postfix/main.cf:

mydestination = SYSTEMHOSTNAME, localhost, proxy:pgsql:/etc/postfix/pgsql-domains.cf

In /etc/postfix/pgsql-domains.cf:


In PostgreSQL DB system and the mail database:

CREATE TABLE domains (
    domainname text not null;
ALTER TABLE domains OWNER TO mailreader;

Then you just have to insert values into the domains table to define the additional domains serviced by the system so that LMTP doesn’t fail lookups.

How does the aliases table work? Entering a username or a full email in the alias column does not allow emails to be sent to this person. Must the account being aliased exist in the users table?

I’m getting the “Relative home directory paths not supported” error too. I tried removing “‘/home/mailboxes/home/’||maildir as home,” as suggested in the comments but I get another error: “User initialization failed: Initializing mail storage from mail_location setting failed: Ambiguous mail location setting, don’t know what to do with it: 0 (try prefixing it with mbox: or maildir:)”

Any idea how to add virtual mailboxes of another host? For example if I’d like to host user1@example1.com and user2@example2.com. Thanks

Lukas, why are you recommending postgresql instead of a passwd file, which Dovecot also supports? I’m trying to understand the pros and cons of each for my own mail server. It seems to me that for a list of users, passwords, and maildirs that is updated occasionally by the administrator, the benefits of using a SQL database aren’t worth the additional complexity of administering a SQL server.

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