ISP Mail Server HowTo

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Revision as of 21:58, 27 January 2010 by Ttrask (talk | contribs) (Cleanup - don't move acf files, fix openssl command line, but lighttpd still will not start)
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A Full Service Mail Server

The goal of this document is to describe how to set up postfix, dovecot, clamav, dspam, roundecube, and postfixadmin for a full-featured "ISP" level mail server.

The server must provide:

  • multiple virtual domains
  • admins for each domain (to add/remove virtual accounts)
  • Quota support per domain / account
  • downloading email via IMAP / IMAPS / POP3 / POP3S
  • relaying email for authenticated users with TLS or SSL (Submission / SMTPS protocol)
  • Standard filters (virus/spam/rbl/etc)
  • Web mail client
  • Value Add services

Set up Lighttpd + PHP

PostfixAdmin needs php pgpsql and imap modules, so we do it in this step.

 apk add lighttpd php php-pgsql php-imap

Stop and remove mini_httpd, and move ACF to lighttpd; We are setting this up to be a mult-domain virtual web server:

 mkdir -p /var/www/domains/
 ln -s /usr/share/acf/www /var/www/domains/

Edit /etc/lighttpd/mod_cgi.conf to serve haserl files by adding a "" => "" cgi handler

$HTTP["url"] =~ "^/cgi-bin/" {
    # disable directory listings
    dir-listing.activate = "disable"
    # only allow cgi's in this directory
    cgi.assign = (
		".pl"	=>	"/usr/bin/perl",
		".cgi"	=>	"/usr/bin/perl",
		"" => ""

Edit /etc/lighttpd/mod_fastcgi.conf to serve php scripts

server.modules += ("mod_fastcgi")
fastcgi.server = ( ".php" => ((
                   "socket" =>  "/var/run/lighttpd/lighttpd-fastcgi-php-" + PID + ".socket"
                    "bin-path" => "/usr/bin/php-cgi"

Add these lines to /etc/lighttpd/lighttpd.conf to point to the new document root, and set it up to listen on port 443:

simple-vhost.server-root   = "/var/www/domains/"
simple-vhost.default-host  = "/"
simple-vhost.document-root = "www/"
$SERVER["socket"] == "[ip_address_of_server]" {
ssl.engine    = "enable"
ssl.pemfile   = "/etc/lighttpd/server-bundle.pem"   = "/etc/lighttpd/ca-crt.pem"

Get a web certificate, and install it. If you want to use a self-signed cert, you can use Generating SSL certs with ACF or Generating SSL certs with ACF 1.9. If you create a certificate with ACF, you can create the "server-bundle.pem" and the "ca-crt.pem" file with these commands:

 openssl pkcs12 -nocerts -nokeys -cacerts -in certificate.pfx  -out /etc/lighttpd/ca-crt.pem
 openssl pkcs12 -nodes -in certifcate.pfx -out /etc/lighttpd/server-bundle.pem
 chown root:root /etc/lighttpd/server-bundle.pem
 chmod 400 /etc/lighttpd/server-bundle.pem

Note: The server certifcate and key are in the server-bundle.pem file, so it is critical that the file be read-only by user "root".

Stop and remove mini_httpd; start lighttpd, test

 /etc/init.d/mini_httpd stop
 rc-update del mini_httpd
 apk del mini_httpd
 rc-update add lighttpd
 /etc/init.d/lighttpd start

At this point you should be able to see ACF being served with lighttpd:

Install Postgresql

Add get and configure postgresql

 apk add acf-postgresql postgresql-client
 /etc/init.d/postgresql setup
 /etc/init.d/postgresql start
 rc-update add postgresql

At this point any user can connect to the sql server with "trust" mechanism. If you want to enforce password authentication (you probably do) edit /var/lib/postgresql/8.4/data/pg_hba.conf

 Editme: What should we recommend?

Create the postfix database:

 psql -U postgres
  create user postfix with password '******';
  create database postfix owner postfix;
  \c postfix
  create language plpgsql;

(Of course, use your selected password where ******* is shown above.)

Install PostfixAdmin

We are going to install the postfix admin web front-end before we install the mail server. This just creates an interface to populate the SQL tables that postfix and dovecot will use.

Download PostfixAdmin from Sourceforge. When these instructions were written, 2.3 was the current release, so:

tar zxvf postfixadmin_2.3.tar.gz
mkdir /var/www/domains/
mv postfixadmin-2.3/* /var/www/domains/
rm -rf postfixadmin*

Edit /var/www/domains/ and modify at least these lines:

$CONF['configured'] = true;
$CONF['setup_password'] = ;  << Don't change this yet
$CONF['database_type'] = 'pgsql';
$CONF['database_host'] = 'localhost';
$CONF['database_user'] = 'postfix';
$CONF['database_password'] = '*****';   << The password you chose above
$CONF['database_name'] = 'postfix';
$CONF['database_prefix'] = ;
$CONF['database_prefix'] = ;
$CONF['database_tables'] = array (
$CONF['admin_email'] = '';  << Your email address 
$CONF['encrypt'] = 'md5crypt';
$CONF['authlib_default_flavor'] = 'md5raw';
$CONF['dovecotpw'] = "/usr/sbin/dovecotpw";
$CONF['domain_path'] = 'YES';
$CONF['domain_in_mailbox'] = 'NO';
$CONF['aliases'] = '10';                       
$CONF['mailboxes'] = '10';
$CONF['maxquota'] = '10';
$CONF['quota'] = 'YES';
$CONF['quota_multiplier'] = '1024000';
$CONF['alias_control'] = 'YES';
$CONF['alias_control_admin'] = 'YES';
$CONF['special_alias_control'] = 'YES';
$CONF['fetchmail'] = 'NO';
$CONF['user_footer_link'] = "";
$CONF['footer_link'] = '';
$CONF['used_quotas'] = 'YES';                     
$CONF['new_quota_table'] = 'YES';

Go to

Create the password hash, add it to the file

Go back to

Create superadmin, create a mail domain or other, as desired.

Install Postfix

Create a user for the virtual mail delivery, and get its uid/gid (you'll need the numeric uid/gid for postfix)

adduser vmail -H -D -s /bin/false
grep vmail /etc/passwd

(In examples below, we use 1006/1006 for the uid/gid)

Create the mail directory, and assign vmail as the owner

mkdir -p /var/mail/domains
chown -R vmail:vmail /var/mail/domains

Install postfix

apk add acf-postfix postfix-pgsql

Edit the /etc/postfix/ file Here's an example:                                                                                                                                  

mydestination = localhost.$mydomains, localhost                                 
mynetworks_style = subnet                                                                    
mynetworks =                                                                     
virtual_mailbox_domains = proxy:pgsql:/etc/postfix/sql/               
virtual_alias_maps = proxy:pgsql:/etc/postfix/sql/,                     

virtual_mailbox_maps = proxy:pgsql:/etc/postfix/sql/,                 

virtual_mailbox_base = /var/mail/domains/                                                          
virtual_gid_maps = static:1006                                                                     
virtual_uid_maps = static:1006                                                                     
virtual_minimum_uid = 100                                                                          
virtual_transport = virtual     

# This next command means you must create a virtual
# domain for the host itself - ALL mail goes through
# The virtual transport

mailbox_transport = virtual
local_transport = virtual                                                                    
local_transport_maps = $virtual_mailbox_maps                                                 

smtpd_helo_required = yes                                                                          
disable_vrfy_command = yes                                                                         
message_size_limit = 10240000                                                                      
queue_minfree = 51200000                                                                           

smtpd_sender_restrictions =                                                                        

smtpd_recipient_restrictions =                                                                     

smtpd_data_restrictions = reject_unauth_pipelining    

# we will use this later - This prevents cleartext authentication
# for relaying
smtpd_tls_auth_only = yes 

Now we need to create a *bunch* of files so that postfix can get the delivery information out of sql. Here's a shell script to create the scripts. Change PGPW to the password for the postfix user of the postfix SQL database.

cd /etc/postfix
mkdir sql
                                                                                                                             cat - <<EOF >sql/
password = $PGPW                                                             
hosts = localhost                                                            
dbname = postfix
query = Select goto From alias,alias_domain where alias_domain.alias_domain = '%d' and alias.address = '@' ||  alias_domain.target_domain and = true and true 

cat - <<EOF >sql/                  
password = $PGPW                                                             
hosts = localhost                                                            
dbname = postfix                                                             
query = Select maildir from mailbox,alias_domain where alias_domain.alias_domain = '%d' and mailbox.username = '%u' || '@' || alias_domain.target_domain and = true and
cat - <<EOF >sql/                          
password = $PGPW                                                             
hosts = localhost                                                            
dbname = postfix                                                             
query = select goto from alias,alias_domain where alias_domain.alias_domain='%d' and alias.address = '%u' || '@' || alias_domain.target_domain and true and true

cat - <<EOF >sql/                                 
password = $PGPW                                                             
hosts = localhost                                                            
dbname = postfix                                                             
query = Select goto From alias Where address='%s' and active ='1'            
cat - <<EOF >sql/                               
password = $PGPW                                                             
hosts = localhost                                                            
dbname = postfix                                                             
query = Select domain from domain where domain='%s' and active='1'
cat - <<EOF >sql/                               
password = $PGPW                                                             
hosts = localhost                                                            
dbname = postfix                                                             
query = Select maildir from mailbox where username='%s' and active=true      
chown -R postfix:postfix sql
chmod 640 sql/*

At this point you should be able to start up postfix

newaliases  # so postfix is happy...
/etc/init.d/postfix start
rc-service add postfix

Create a domain in PostfixAdmin and test

create a domain for the local box (e.g. Create the alias accounts

From the machine, send a test message:

sendmail -t
subject: test

In /var/log/mail.log (or /var/log/messages, if you still have busybox syslogd running) you should see the message queued. The message should be in /var/mail/domains/

Install Dovecot

Dovecot is the POP3/IMAP server to retrieve mail.

As before, we install dovecot:

apk add acf-dovecot dovecot-pgsql

edit /etc/dovecot.conf

# Select only the protocols you wish to support - all are listed in the next line
protocols               =       imap imaps pop pop3s
log_path                =       /var/log/dovecot.log
info_log_path           =       /var/log/dovecot-info.log
disable_plaintext_auth  =       no
# Authenticated IMAP
ssl                     =       yes
ssl_cert_file           =       /etc/lighttpd/server-bundle.pem
ssl_key_file            =       /etc/lighttpd/server-bundle.pem
auth_verbose            =       yes
auth_debug              =       no
mail_location           =       maildir:/var/mail/domains/%d/%n
auth default    {
       mechanisms = plain
       passdb sql {
               args = /etc/dovecot/dovecot-sql.conf
       userdb static {
               args =  uid=1006 gid=1006 home=/var/mail/domains/%d/%n

We need a certificate for SSL/TLS authentication, so in the example above, we use the lighttpd cert. That way when the cert is renewed/replaced, Dovecot will have access to the new cert as well.

Create the /etc/dovecot/dovecot-sql.conf file:

driver = pgsql
connect = host=localhost dbname=postfix user=postfix password=********
password_query = select username,password from mailbox where local_part = '%n' and domain = '%d'
default_pass_scheme =  MD5-CRYPT

Again, change the password above to your postfix user password, and protect the file from prying eyes:

chown root:root /etc/dovecot/dovecot-sql.conf
chmod 600 /etc/dovecot/dovecot-sql.conf

Start dovecot

/etc/init.d/dovecot start
rc-update add dovecot


Make sure your firewall allows in ports 25(SMTP) 110 (POP3), 995 (POP3S), 143(IMAP), 993(IMAPS), or whatever subset you support.

At this point, you should be able to:

* Create a new domain and add users with PostfixAdmin
* Send mail to those users via SMTP to port 25
* Retrieve mail using the user's full email and password (e.g. username:  password: ChangeM

Value Add Features

If you followed the guide above, you now have a functional mail server with many interconnected parts. The features below assume that the server is already running as described above. You should be able to add any or all of these features below to further enhance the mail service.

Virus Scanning

This procedure uses clamav and the postfix content_filter mechanism to scan inbound and outbound email for viruses. Infected emails are dropped. Clean emails are tagged with a "scanned by clamav" header.

  • Install clamav and clamsmtp:
apk add acf-clamav clamsmtp
  • Edit the /etc/clamav/clamd.conf file if desired (not necessary in most cases)
  • Edit /etc/clamsmtpd.conf and verify the following lines
OutAddress: 10026
Header: X-Virus-Scanned: ClamAV using ClamSMTP
Action: drop
User: clamav                                                      
  • Start the daemons
rc-update add clamd
rc-update add freshclam
rc-update add clamsmtp
/etc/init.d/clamd start
/etc/init.d/freshclam start
/etc/init.d/clamsmtp start
  • Verify clamsmtp is listening on port 10025:
netstat -anp | grep clamsmtp
content_filter = scan:[]:10025                                                      
    • edit /etc/postfix/ and add
# AV scan filter (used by content_filter)
scan      unix  -       -       n       -       16      smtp
        -o smtp_send_xforward_command=yes
        -o smtp_enforce_tls=no
# For injecting mail back into postfix from the filter inet  n -       n       -       16      smtpd
        -o content_filter=
        -o receive_override_options=no_unknown_recipient_checks,no_header_body_checks
        -o smtpd_helo_restrictions=
        -o smtpd_client_restrictions=
        -o smtpd_sender_restrictions=
        -o smtpd_recipient_restrictions=permit_mynetworks,reject
        -o mynetworks_style=host
        -o smtpd_authorized_xforward_hosts=
  • postfix reload
  • Send and email into a local virtual domain - it should have the X-Virus-Scanned: ClamAV using ClamSMTP header.

Relay for Authenticated Users

As configured above, the mail server accepts email from the Internet, but it does not relay email. If it is a perimeter exchanger for a protected network, then you can add the protected networks to the mynetworks configuration line in /etc/postfix/

This configuration change allows remote users to authenticate against the mail server and relay through it. The rules for relaying are:

  • Only authenticated users can relay
  • Authentication Credentials must be encrypted with TLS or SSL
  • Allow Submission and SMTPS ports for relaying (many consumer networks block port 25 - SMTP by default)

The process uses the dovecot authentication mechanism (used with IMAPS) to authenticate users before they are allowed to relay through postfix.

  • Edit /etc/dovecot/dovecot.conf and add:
# this is for postfix SASL (authenticated users can relay through us)
socket listen {
               client {
                       path    = /var/spool/postfix/private/dovecot-auth.sock
                       mode    = 0660
                       user    = postfix
                       group   = postfix
  • Restart dovecot
/etc/init.d/dovecot restart
  • Edit /etc/postfix/ and add:
# TLS Stuff -- since we allow SASL with tls *only*, we have to set up TLS first                    

smtpd_tls_cert_file = /etc/lighttpd/server-bundle.pem
smtpd_tls_key_file = /etc/lighttpd/server-bundle.pem
smtpd_tls_CAfile = /etc/lighttpd/ca-crt.pem
# If tls_security_level is set to "encrypt", then SMTP rejects 
# unencrypted email (e.g. normal mail) which is bad.
# By setting it to "may" you get TLS encrypted mail from google, slashdot, and other 
# interesting places.  Check your logs to see who
smtpd_tls_security_level = may
# Log info about the negotiated encryption levels
smtpd_tls_received_header = yes
smtpd_tls_loglevel = 1

# SASL - this allows senders to authenticiate themselves
# This along with "permit_sasl_authenticated" in smtpd_recipient_restrictions allows relaying
smtpd_sasl_type = dovecot
smtpd_sasl_path = private/dovecot-auth.sock
smtpd_sasl_auth_enable = yes
smtpd_sasl_authenticated_header = yes
smtpd_tls_auth_only = yes
  • Edit /etc/postfix/ and enable the submission and smtps transports. They are probably already at the top of your file, just commented out:
submission inet n       -       n       -       -       smtpd
  -o smtpd_tls_security_level=encrypt
  -o smtpd_sasl_auth_enable=yes
  -o smtpd_client_restrictions=permit_sasl_authenticated,reject
  -o milter_macro_daemon_name=ORIGINATING
smtps     inet  n       -       n       -       -       smtpd
  -o smtpd_tls_security_level=encrypt
  -o smtpd_tls_wrappermode=yes
  -o smtpd_sasl_auth_enable=yes
  -o smtpd_client_restrictions=permit_sasl_authenticated,reject
  -o milter_macro_daemon_name=ORIGINATING
  • Verfiy submission and smtps are defined in /etc/services
grep "submission\|ssmtp" /etc/services
submission	587/tcp				# mail message submission
submission	587/udp
smtps		465/tcp		ssmtp		# smtp protocol over TLS/SSL
smtps		465/udp		ssmtp
  • Restart postfix
postfix reload

At this point, you should be able to set up a mail client to relay through the server with TLS (port 587) or SSL (port 465) Note that "plain" authentication is used because the underlying link is encrypted. For example, in Thunderbird leave "secure authentication" unchecked, and choose STARTTLS (or TLS) for the connection security.

log rotation

Special thanks to DHughes for providing a 3 page email on how to set up postgres,postfix,PostfixAdmin,dovecot and roundcube. It was the clearer than all the other guides available on the Net. Thanks!