postfix virtual domain on specific IP address

Question

We are running postfix with single domain (example.com) currently and we have appropriate PTR record for that.

Now we want to add one more domain but i want to isolate that domain totally, Even i want to isolate PTR record too. so we added new public IP address in same server and added PTR entry to abc.com

1. example.com - 1.1.1.1
2. abc.com - 2.2.2.2

How i am going to tell postfix run example.com on 1.1.1.1 ip address and abc.com on 2.2.2.2

so from outside if someone try to telnet on 25 port he get different appropriate domain for relevant IP.

$ telnet mail.example.com 25
Trying ::1...
Connected to mail.example.com.
Escape character is '^]'.
220 mail.example.com ESMTP Postfix

And for abc.com

$telnet mail.abc.com 25
Trying ::1...
Connected to mail.abc.com.
Escape character is '^]'.
220 mail.abc.com ESMTP Postfix

Answer 1

Following should work for postfix equal or higher than 2.7.

You need to modify /etc/postfix/master.cf, change the line smtp inet n - n - - smtpd to something like this:

domain1 unix -       -       n       -       -       smtp
      -o syslog_name=postfix-mail.example.com
      -o smtp_helo_name=mail.example.com
      -o smtp_bind_address=1.1.1.1

domain2 unix -       -       n       -       -       smtp
      -o syslog_name=postfix-mail.abc.com     
      -o smtp_helo_name=mail.abc.com
      -o smtp_bind_address=2.2.2.2
#...

Then in /etc/posfix/main.cf you will need to remove old transport maps (if any) afterwards add sender_dependent_default_transport_maps for exmaple:

sender_dependent_default_transport_maps = hash:/etc/postfix/sender_transport

In /etc/postfix/sender_transport you need to add:

@example.com    domain1:
@abc.com    domain2:
#...

Then you need to create a hash db from the sender_transport file, with command:

postmap hash:/etc/postfix/sender_transport

Restart postfix to pickup the changes.

You could also move the transport maps to a database and create a table for the domains etc. This is just a basic setup but it should give you some ideas.