Postfix IPv6 Support


Postfix 2.2 introduces support for the IPv6 (IP version 6) protocol. IPv6 support for older Postfix versions was available as an add-on patch. The section "Compatibility with Postfix <2.2 IPv6 support" below discusses the differences between these implementations.

The main feature of interest is that IPv6 uses 128-bit IP addresses instead of the 32-bit addresses used by IPv4. It can therefore accommodate a much larger number of hosts and networks without ugly kluges such as NAT. A side benefit of the much larger address space is that it makes random network scanning impractical.

Postfix uses the same SMTP protocol over IPv6 as it already uses over the older IPv4 network, and does AAAA record lookups in the DNS in addition to the older A records. Information about IPv6 can be found at

This document provides information on the following topics:

Supported Platforms

Postfix version 2.2 supports IPv4 and IPv6 on the following platforms:

On other platforms Postfix will simply use IPv4 as it has always done.

See below for tips how to port Postfix IPv6 support to other environments.


Postfix IPv6 support introduces two new configuration parameters, and introduces an important change in address syntax notation in match lists such as mynetworks or debug_peer_list.

Postfix IPv6 address syntax is a little tricky, because there are a few places where you must enclose an IPv6 address inside "[]" characters, and a few places where you must not. It is a good idea to use "[]" only in the few places where you have to. Check out the postconf(5) manual whenever you do IPv6 related configuration work with Postfix.

NOTE: when configuring Postfix match lists such as mynetworks or debug_peer_list, you must specify IPv6 address information inside "[]" in the parameter value and in files specified with a "/file/name" pattern. IPv6 addresses contain the ":" character, and would otherwise be confused with a "type:table" pattern.

Known Limitations

Compatibility with Postfix <2.2 IPv6 support

Postfix version 2.2 IPv6 support is based on the Postfix/IPv6 patch by Dean Strik and others, but differs in a few minor ways.

IPv6 Support for unsupported platforms

Getting Postfix IPv6 working on other platforms involves the following steps:

If none of all this produces a usable result, send email to the mailing list and we'll try to help you through this.


The following information is in part based on information that was compiled by Dean Strik.