Postfix Bind Sender Domain To Dedicated Outgoing IP Address

email, postfix, sendmail, smtp Add comments

Jan 022010

Recently there have been requests for sending mail with source IP addresses that depend on the envelope sender, it’s very usefull to protect IP-based domain reputations of different customers.

New Feature in postfix postfix-2.7-20091209 is sender_dependent_default_transport_maps

sender_dependent_default_transport_maps (default: empty)

    A sender-dependent override for the global default_transport parameter setting.
    The tables are searched by the envelope sender address and @domain.
    A lookup result of DUNNO terminates the search without overriding the global default_transport parameter setting.
    This information is overruled with the transport(5) table.

    Note: this overrides default_transport, not transport_maps, and therefore the expected syntax is that of default_transport.
          This feature does not support the transport_maps syntax for null transport, null nexthop, or null email addresses.

    For safety reasons, this feature does not allow $number substitutions in regular expression maps.

    This feature is available in Postfix 2.7 and later.

Create file called sdd_transport_maps.regexp:

/@customer1-dom\.tld$/		customer1:
/@customer2-dom\.tld$/		customer2:
/@customer3-dom\.tld$/		customer3:
..... next .....

In master.cf create special transport called customer1, customer2, customer3….and so on

customer1  unix -       -       n       -       -       smtp
   -o smtp_bind_address=1.1.1.1
   -o smtp_helo_name=customer1-dom.tld
   -o syslog_name=postfix-customer1

customer2  unix -       -       n       -       -       smtp
   -o smtp_bind_address=1.1.1.2
   -o smtp_helo_name=customer2-dom.tld
   -o syslog_name=postfix-customer2

customer3  unix -       -       n       -       -       smtp
   -o smtp_bind_address=1.1.1.3
   -o smtp_helo_name=customer3-dom.tld
   -o syslog_name=postfix-customer3

..... next .....

In main.cf add sender_dependent_default_transport_maps line:

sender_dependent_default_transport_maps = regexp:/etc/postfix/sdd_transport_maps.regexp

Don’t forget to create ip aliasing for each ip address in smtp_bind_address

reload postfix

# postfix reload

31 Responses to “Postfix Bind Sender Domain To Dedicated Outgoing IP Address”

Comments (31)

Sachin says:

May 30, 2012 at 4:15 am

Hi there,

Thanks for this article, it seems to be the ONLY solution to defining domain specific outbound address in postfix.

However, I do not understand the line “Don’t forget to create ip aliasing for each ip address in smtp_bind_address”

IP aliasing is to create aliases for network interface eth0 e.g. eth0:1 -> x.x.x.1, eth0:2 -> x.x.x.2 etc which is working fine (tested apache virtual hosts). But then what would be the value for the smtp_bind_address parameter in main.cf?

Should it be smtp_bind_address = {IP Address of eth0}?

Reply
- leenoux says:
  
  May 30, 2012 at 7:29 am
  
  when you bind an address using smtp_bind_address without real/alias address postfix would be happily throw errors
  the purpose is when user@customer1-dom.tld send an email, it will be routed to customer1: and statically bound to ip address 1.1.1.1
```
customer1  unix -       -       n       -       -       smtp
   -o smtp_bind_address=1.1.1.1
```
  hope that’s help
  Reply
Joe V says:

November 8, 2012 at 4:55 am

Exactly what I needed. It worked perfectly first try. Thanks!!

Reply
Esteban says:

December 17, 2012 at 10:57 pm

Does this means that it will generate a specific outbound queue for those transports?

Reply
- leenoux says:
  
  December 18, 2012 at 9:02 am
  
  no, in order to make multiple queue you must use multiple instances
  
  Reply
David says:

January 23, 2013 at 12:05 am

Unfortunately i’m not having as much luck as others, though i’m doing exactly what’s shown here and other sites.

My postfix version 2.9.5 on CentOS 6.3 blatantly refuses to bind IPs based on these headers. It will always use the eth0 IP and not the eth0:1, eth0:2, etc.

I’ve tried using regexp and shown in this example as well as hash table but same result.

master.cf (eth0 = 1.1.1.1, eth0:1 = 1.1.1.2, eth0:2 = 1.1.1.3)

smtp inet n - n - - smtpd pickup fifo n - n 60 1 pickup cleanup unix n - n - 0 cleanup qmgr fifo n - n 300 1 qmgr tlsmgr unix - - n 1000? 1 tlsmgr rewrite unix - - n - - trivial-rewrite bounce unix - - n - 0 bounce defer unix - - n - 0 bounce trace unix - - n - 0 bounce verify unix - - n - 1 verify flush unix n - n 1000? 0 flush proxymap unix - - n - - proxymap proxywrite unix - - n - 1 proxymap smtp unix - - n - - smtp relay unix - - n - - smtp -o smtp_fallback_relay= showq unix n - n - - showq error unix - - n - - error retry unix - - n - - error discard unix - - n - - discard local unix - n n - - local virtual unix - n n - - virtual lmtp unix - - n - - lmtp anvil unix - - n - 1 anvil scache unix - - n - 1 scache
one unix - - n - - smtp -o smtp_bind_address=1.1.1.2 -o smtp_helo_name=mail1.one.com
two unix - - n - - smtp -o smtp_bind_address=1.1.1.3 -o smtp_helo_name=mail1.one.com

main.cf
sender_dependent_default_transport_maps = regexp:/etc/postfix/sdd_transport_maps.regexp

sdd_transport_maps.regexp
/@one\.com$/ one: /@two\.com$/ two:

Yeah, i’ve postmapped all these files, reloaded postfix, even restarted it and then restarted the server. my postfix also indeed supports regexp.

Is there any debugging i can enable to figure this out?

Reply
- leenoux says:
  
  January 23, 2013 at 9:04 am
  
  there’s nothing to do with postfix map, does your ip aliasing really up?show me postfix errors | warning log
  
  Reply