Setting up postfix with virtual domains

Postfix on 1.9

General

The idea is to create a postfix config to host multiple maildomains.
I want to document both how it's set up and how it's maintained.

When you are done with postfix installation you could proceed and install (depending on your needs)

• clamav
• gross
• dovecot
• Other email related applications

Have a look at Hosting_services_on_Alpine#Mail for various alternatives and instructions.

Initial Setup

Burn alpine-1.9.3-x86.iso (or higher) on a CD and boot the machine.
Suggestion: Follow notes on Setting_up_a_ssh-server to be able to remotely administer this box.

Postfix

Install

apk_add postfix

Prepare

We need to create a user on this system that has rights to read/write mail on you system.
Let's call this user vmail (you can choose another name if you like).
You will get prompted for a password.

adduser vmail

Now we need to know what gid/uid that user got.
Take notes on the numbers, you will need the in the upcoming configuration (in my case I got uid/gid '1001').

grep vmail /etc/passwd

This newly-created user will need permissions in the mail group.
Edit /etc/group and add vmail to the postdrop group. Se example below:

postdrop:x:208:vmail

Create missing dirs

Seems we are missing /var/spool/mail so we need to create it

mkdir /var/spool/mail

Create virtual maildir

In the upcoming configuration we are going to specify /var/spool/mail/vhosts/ as the virtual_mailbox_base so we need to create it.

mkdir /var/spool/mail/vhosts

And we need to give permissions to our vmail user so he can read/write in this folder.

chown vmail:postdrop /var/spool/mail/vhosts

Configuration

FIXME: The following configuration needs some more work

/etc/postfix/main.cf

These are the variables that varies from the defaults

## These settings differers from the default config ##
soft_bounce = yes   # For testing
myhostname = mail.example.net
mydomain = example.net
myorigin = $mydomain
mydestination = localhost, mail.localdomain, localhost.localdomain, localdomain   # See 'virtual_mailbox_domains' for more information
mynetworks = 192.168.10.0/24, 127.0.0.0/8
relayhost =
in_flow_delay = 1s
home_mailbox = Maildir/
mail_spool_directory = /var/spool/mail
smtpd_banner = $myhostname ESMTP $mail_name ($mail_version)

## The following is added to the config ##
local_transport = virtual
virtual_mailbox_domains = example.net
virtual_mailbox_base = /var/spool/mail/vhosts
virtual_mailbox_maps = hash:/etc/postfix/vmailbox
virtual_minimum_uid = 100
virtual_uid_maps = static:1001
virtual_gid_maps = static:1001
virtual_alias_maps = hash:/etc/postfix/valias

smtpd_helo_required = yes
disable_vrfy_command = yes
smtpd_recipient_restrictions =
        reject_unauth_pipelining,
        permit_sasl_authenticated,
        permit_mynetworks,
        reject_invalid_hostname, reject_non_fqdn_hostname,
        reject_non_fqdn_sender, reject_non_fqdn_recipient,
        reject_unknown_sender_domain, reject_unknown_recipient_domain,
        reject_unauth_destination, 
        permit
smtpd_data_restrictions = reject_unauth_pipelining, permit

/etc/postfix/valias

postmaster@example.net user1@example.net
hostmaster@example.net user2@example.net

/etc/postfix/vmailbox

user1@example.net      example.net/user1/
user2@example.net      example.net/user2/
@example.net           example.net/catchall #everyone else doesn't match rule above

Create DB's

Once you created the above config-files, you need to make generate some DB's

postmap /etc/postfix/vmailbox
postmap /etc/postfix/valias

I am not 100% if the next command is needed, but I think that you need to create the 'aliases' DB.

postmap /etc/postfix/aliases

Start postfix

It's time to start. Hopefully it works!

/etc/init.d/postfix start

Debugging

In case something goes wrong you should have a look in your syslog.
Personally I use to tail the logfile while debugging

tail -f /var/log/messages

Add/Remove mailboxes

In the above examples we used /etc/postfix/vmailbox to store our list of mailboxes.
To add/remove a mailbox, you need to edit this file and then rebuild the DB.

vi /etc/postfix/vmailbox
postmap /etc/postfix/vmailbox

Now we have done our re-configuration and we want postfix to start using the new settings.

postfix reload