Re: proxy_interfaces understanding

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proxy_interfaces understanding
\ Joseph L. Casale (16 Jan 2008)
. \ Victor Duchovni (17 Jan 2008)

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Subject:	Re: proxy_interfaces understanding
Group:	Postfix-users
From:	Victor Duchovni
Date:	17 Jan 2008

On Wed, Jan 16, 2008 at 04:40:58PM -0700, Joseph L. Casale wrote:

> Hi,
> If postfix runs as a gateway without local mail delivery and merely forwards mail to my real mailserver while sitting behind a NAT device I see I should have proxy_interfaces configured with the real external IP. I am trying to understand what postfix does internally with this info and can't seem to find any documentation that states anymore then this will prevent mail loops when used on a backup mx server.
>
> Can someone point me in the right direction?

The short answer is that you should let Postfix know which IP addresses
route mail into the host it is running on. The set of reasons for this
may vary over time, so this explanation is generally sufficient.

If you want to understand internals, the Postfix SMTP delivery agent
truncates the MX host list for a destination at hosts whose preference
is better than that of the current machine, and because a host can have
many names, Postfix compares the addresses of each MX host to the addresses
(including proxy) of the host it is running on.

--
Viktor.

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