I've installed postfix 2.11.3 and we have multiple IP addresses on our server which we want to host two domains, isolated and running on their own IPs.

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

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

Following transporter /etc/postfix/sender_transport also defined in main.cf:

@abc.com    domain1:
@xyz.com    domain2:

After restarting postfix, it stopped listening on port 25:

[[email protected]]# telnet 1.1.1.1 25
Trying 1.1.1.1...
telnet: connect to address 1.1.1.1: Connection refused

But if I use following line in master.cf it listen on 25 and i can see banner if i telnet:

1.1.1.1:smtp inet  n - n - - smtpd -o myhostname=mail.abc.com 
2.2.2.2:smtp inet  n - n - - smtpd -o myhostname=mail.xyz.com

But I want to tell my mail server when you send out email use specific domain just like sender_transport

What i am doing wrong?

Notes:

I have removed following line from master.cf and replaced with above domain1 and domain2:

smtp      inet  n       -       n       -       -       smtpd

Solution - Postfix version 2.7 or above required:

/etc/postfix/master.cf

#smtp      inet  n       -       n       -       -       smtpd
127.0.0.1:smtp inet  n     -       n       -       -       smtpd
      -o syslog_name=postfix-localhost
      -o smtp_helo_name=localhost
      -o smtp_bind_address=127.0.0.1
      -o myhostname=localhost

65.xxx.xxx.100:smtp inet  n     -       n       -       -       smtpd
      -o syslog_name=postfix-mail.abc.com
      -o smtp_helo_name=mail.abc.com
      -o smtp_bind_address=65.xxx.xxx.100
      -o myhostname=mail.abc.com

65.xxx.xxx.200:smtp inet  n     -       n       -       -       smtpd
      -o syslog_name=postfix-mail.xyz.com
      -o smtp_helo_name=mail.zyx.com
      -o smtp_bind_address=65.xxx.xxx.200
      -o myhostname=mail.xyz.com

abc-out  unix -       -       n       -       -       smtp
   -o smtp_bind_address=65.xxx.xxx.100
   -o smtp_helo_name=mail.abc.com
   -o syslog_name=postfix-mail.abc.com

xyz-out  unix -       -       n       -       -       smtp
   -o smtp_bind_address=65.xxx.xxx.200
   -o smtp_helo_name=mail.xyz.com
   -o syslog_name=postfix-mail.xyz.com

/etc/postfix/main.cf

sender_dependent_default_transport_maps = hash:/etc/postfix/sender_transport

/etc/postfix/sender_transport

# Use source IP - 65.xxx.xxx.100
@abc.com                abc-out:
@example.com            abc-out:

# Use source IP - 65.xxx.xxx.200 
@xyz.com                xyz-out:

Run command to generate hash db

postmap hash:/etc/postfix/sender_transport

Restart/Reload postfix

service postfix reload

Testing

[root@localhost ~]# telnet 65.xxx.xxx.200 25
Trying 65.xxx.xxx.200...
Connected to 65.xxx.xxx.200.
Escape character is '^]'.
220 mail.xyz.com ESMTP Postfix

Sending email test

[root@localhost ~]# telnet localhost 25
Trying ::1...
telnet: connect to address ::1: Connection refused
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 localhost ESMTP Postfix
helo localhost
250 localhost
mail from: [email protected]
250 2.1.0 Ok
rcpt to: [email protected]
250 2.1.5 Ok
data
354 End data with <CR><LF>.<CR><LF>
Hello world!
.
250 2.0.0 Ok: queued as 93E708207BA

Got to gmail Inbox > Show Original

Delivered-To: [email protected]
Received: by 10.xxx.xxx.xxx with SMTP id w64csp782609qgd;
        Tue, 9 Dec 2014 09:35:57 -0800 (PST)
X-Received: by 10.xxx.xxx.xxx with SMTP id o28mr4132552yha.168.1418146557180;
        Tue, 09 Dec 2014 09:35:57 -0800 (PST)
Return-Path: <[email protected]>
Received: from mail.xyz.com ([65.xxx.xxx.200])
        by mx.google.com with ESMTPS id n10si743294ykc.114.2014.12.09.09.35.56
        for <[email protected]>
        (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128);
        Tue, 09 Dec 2014 09:35:56 -0800 (PST)
...
...
Message-Id: <[email protected]>
Date: Tue,  9 Dec 2014 12:37:11 -0500 (EST)
From: [email protected]

Hello world!

Voila!! see it used 65.xxx.xxx.200 IP address to sent out email..

Received: from mail.xyz.com ([65.xxx.xxx.200])