ISP Mail Server HowTo
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
Configure DNS
This server will host three separate virtual domains on the same web server. They will be distinguished by their domains, so you must choose three domains for the three separate services:
- ACF - Alpine Configuration Framework for managing the server
- PostfixAdmin - for managing the postfix installation
- RoundCube - for accessing individual mailboxes
Choose three different domains (herein knows is ACF_DOMAIN, POSTFIXADMIN_DOMAIN, and ROUNDCUBE_DOMAIN) and configure DNS for all three to point to the IP address of your host.
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 multi-domain virtual web server (replace ACF_DOMAIN with the actual domain):
mkdir -p /var/www/domains/ACF_DOMAIN ln -s /usr/share/acf/www /var/www/domains/ACF_DOMAIN/www
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",
"" => ""
)
}
Add these lines to /etc/lighttpd/lighttpd.conf to point to the new document root, and set it up to listen on port 443 (replace ROUNDCUBE_DOMAIN with the roundcube domain and ip_address_of_server with the actual IP address):
simple-vhost.server-root = "/var/www/domains/"
simple-vhost.default-host = "/ROUNDCUBE_DOMAIN/"
simple-vhost.document-root = "www/"
$SERVER["socket"] == "ip_address_of_server:443" {
ssl.engine = "enable"
ssl.pemfile = "/etc/lighttpd/server-bundle.pem"
ssl.ca-file = "/etc/lighttpd/ca-crt.pem"
}
Ensure that the simple_vhosts module is loaded, as well as the cgi config scripts by uncommenting the following lines in /etc/lighttpd/lighttpd.conf
server.modules = (
# other modules may be listed
"mod_simple_vhost",
# other modules may be listed
.
.
.
include "mod_cgi.conf"
include "mod_fastcgi.conf"
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 -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 certificate and key are in the server-bundle.pem file, so it is critical that the file be read-only by user "root".
Editme: We should probably only serve ACF to restricted hosts
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: https://ACF_DOMAIN/
Install Postgresql
Add 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; \q
(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 (replace POSTFIXADMIN_DOMAIN with the actual domain):
wget http://downloads.sourceforge.net/project/postfixadmin/postfixadmin/postfixadmin_2.3.tar.gz tar zxvf postfixadmin_2.3.tar.gz mkdir -p /var/www/domains/POSTFIXADMIN_DOMAIN/www mv postfixadmin-2.3/* /var/www/domains/POSTFIXADMIN_DOMAIN/www rm -rf postfixadmin*
Edit /var/www/domains/POSTFIXADMIN_DOMAIN/www/config.inc.php 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['admin_email'] = 'you@some.email.com'; << 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['vacation'] = 'NO'; $CONF['vacation_control'] ='NO'; $CONF['vacation_control_admin'] = 'NO'; $CONF['create_mailbox_subdirs_prefix']=""; $CONF['quota'] = 'YES'; $CONF['quota_multiplier'] = '1024000'; $CONF['used_quotas'] = 'YES'; $CONF['new_quota_table'] = 'YES'; $CONF['alias_control'] = 'YES'; $CONF['alias_control_admin'] = 'YES'; $CONF['special_alias_control'] = 'YES'; $CONF['fetchmail'] = 'NO'; $CONF['user_footer_link'] = "http://host.example.com"; $CONF['footer_link'] = 'http://host.example.com/postfixadmin/main.php';
Go to http://POSTFIXADMIN_DOMAIN/setup.php
Create the password hash, add it to the config.inc.php file
Go back to http://POSTFIXADMIN_DOMAIN/setup.php
Create superadmin, create a mail domain or other, as desired.
Install Postfix
Create a user for the virtual mail delivery, and get its uid/gid (you'll need the numeric uid/gid for postfix)
adduser vmail -H -D -s /bin/false grep vmail /etc/passwd
(In examples below, we use 1006/1006 for the uid/gid)
Create the mail directory, and assign vmail as the owner
mkdir -p /var/mail/domains chown -R vmail:vmail /var/mail/domains
Install postfix
apk add acf-postfix postfix-pgsql
Edit the /etc/postfix/main.cf file Here's an example:
myhostname=host.example.com
mydomain=example.com
mydestination = localhost.$mydomains, localhost
mynetworks_style = subnet
mynetworks = 127.0.0.0/8
virtual_mailbox_domains = proxy:pgsql:/etc/postfix/sql/pgsql_virtual_domains_maps.cf
virtual_alias_maps = proxy:pgsql:/etc/postfix/sql/pgsql_virtual_alias_maps.cf,
proxy:pgsql:/etc/postfix/sql/pgsql_virtual_alias_domain_maps.cf,
proxy:pgsql:/etc/postfix/sql/pgsql_virtual_alias_domain_catchall_maps.cf
virtual_mailbox_maps = proxy:pgsql:/etc/postfix/sql/pgsql_virtual_mailbox_maps.cf,
proxy:pgsql:/etc/postfix/sql/pgsql_virtual_alias_domain_mailbox_maps.cf
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 =
permit_mynetworks,
reject_non_fqdn_sender,
reject_unknown_sender_domain
smtpd_recipient_restrictions =
reject_non_fqdn_recipient,
reject_unknown_recipient_domain,
permit_mynetworks,
permit_sasl_authenticated,
reject_unauth_destination,
reject_rbl_client dnsbl.sorbs.net,
reject_rbl_client zen.spamhaus.org,
reject_rbl_client bl.spamcop.net
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 PGPW="ChangeMe" cat - <<EOF >sql/pgsql_virtual_alias_domain_catchall_maps.cf user=postfix 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 alias.active = true and alias_domain.active= true EOF cat - <<EOF >sql/pgsql_virtual_alias_domain_mailbox_maps.cf user=postfix 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 mailbox.active = true and alias_domain.active EOF cat - <<EOF >sql/pgsql_virtual_alias_domain_maps.cf user=postfix 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 alias.active= true and alias_domain.active= true EOF cat - <<EOF >sql/pgsql_virtual_alias_maps.cf user=postfix password = $PGPW hosts = localhost dbname = postfix query = Select goto From alias Where address='%s' and active ='1' EOF cat - <<EOF >sql/pgsql_virtual_domains_maps.cf user=postfix password = $PGPW hosts = localhost dbname = postfix query = Select domain from domain where domain='%s' and active='1' EOF cat - <<EOF >sql/pgsql_virtual_mailbox_maps.cf user=postfix password = $PGPW hosts = localhost dbname = postfix query = Select maildir from mailbox where username='%s' and active=true EOF 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. example.com) Create the alias accounts
From the machine, send a test message:
sendmail -t root@example.com subject: test . ^d
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/example.com/root/new
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
Testing
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: user@example.com 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 Listen: 127.0.0.1:10025 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
- Following the clamsmtp instructions
- edit /etc/postfix/main.cf and add:
content_filter = scan:[127.0.0.1]:10025
- edit /etc/postfix/master.cf 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
127.0.0.1:10026 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=127.0.0.0/8
- 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/main.cf
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/main.cf 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/master.cf and enable the submission and smtps transports. They are probably already at the top of your master.cf 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.
Mailbox Quotas
In the default configuration, PostfixAdmin knows about quotas, but they are not enforced. Documentation on the web mentions the vda patch to postifx to enforce quotas. The only bad thing... its a patch. Postfix and Dovecot are both conservative systems, so if the patch isn't in the upstream source, we'll assume there's a good reason. There is a way of using quotas without patches - and it involves using the dovecot's deliver lda for local delivery.
Note: As of Jan 2010, the documention is confusing, with multiple versions of dovecot, PostfixAdmin, and Mysql referenced. These instructions apply to:
- Postgresql 8.4.2
- PostfixAdmin 2.3
- Dovecot 1.2.9
- Postfix 2.6.5
Presumably later versions will work the same, but if not, please update the documentation and versions above.
- Update /etc/dovecot.conf (old lines shown commented out):
# old postfix
# userdb static {
# args = uid=1006 gid=1006 home=/var/mail/domains/%d/%n
# }
# new quota support:
userdb prefetch {
}
userdb sql {
args = /etc/dovecot/dovecot-sql.conf
}
socket listen {
client {
path = /var/spool/postfix/private/dovecot-auth.sock
mode = 0660
user = postfix
group = postfix
}
# These lines below are for the deliver lda
master {
path = /var/run/dovecot/auth-master
mode = 0660
user = vmail
group = vmail
}
}
protocol imap {
mail_plugins = quota imap_quota
}
protocol pop3 {
mail_plugins = quota
}
dict {
quotadict = pgsql:/etc/dovecot/dovecot-dict-quota.conf
}
plugin {
quota = dict:user::proxy::quotadict
}
protocol lda {
postmaster_address = postmaster@host.example.com
mail_plugins = quota
auth_socket_path = /var/run/dovecot/auth-master
sendmail_path = /usr/sbin/sendmail
}
You should already have a socket-> listen-> client section, but it is listed above to show where it goes in relationship to the socket -> listen -> master section
- edit /etc/dovecot/dovecot-sql.conf and replace the user and password queries with the following (you may not have a user_query yet - add it):
password_query = select username as user, password, 1006 as userdb_uid, 1006 as userdb_gid, '*:bytes=' || quota as userdb_quota_rule from mailbox where local_part = '%n' and domain = '%d' user_query = select maildir as home, 1006 as uid, 1006 as gid, '*:bytes=' || quota as quota_rule from mailbox where local_part = '%n' and domain ='%d'
- create /etc/dovecot/dovecot-dict-quota.conf
connect = host=localhost dbname=postfix user=postfix password=********
map {
pattern = priv/quota/storage
table = quota2
username_field =username
value_field = bytes
}
map {
pattern= priv/quota/messages
table = quota2
username_field = username
value_field = messages
}
Side note: The Dovecot Quota Documentation mentions the need for a trigger with pgsql. This was created in the PostfixAdmin install, which is why you instantiated the pgsql language when creating the database. If not, you will need to create the trigger, to reference the quota2 table, not the quota table mentioned in the dovecot docs.
- create a new transport for the dovecot lda. Add the following to /etc/postfix/master.cf:
# The dovecot deliver lda
dovecot unix - n n - - pipe
flags=DRhu user=vmail:vmail argv=/usr/libexec/dovecot/deliver -f ${sender} -d ${user}@${nexthop}
- Edit the /etc/postfix/main.cf. Replace
virtual_transport = virtual
with
virtual_transport = dovecot dovecot_destination_recipient_limit = 1
TODO This will cause over-quota emails to bounce. Which could be a source of backscatter. We need a way of checking quota limits after RBL checking but before the message is accepted in the queue.
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!