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Subject: Re: [2] how to bind smtp client to specific address?
From: Michael Ju. Tokarev (mjttls.msk.ru)
Date: Thu Mar 30 2000 - 06:11:48 CST

Wietse!
Can you consider to include, say, "smtpd_outgoing_address" parameter
into postfix? Sounds like people still asking about this...
This is a trivial addition, but with non-trivial background
(if machine really have multiple interfaces and connections
are made on some of this, not just only one, this should be
turned into map, not single "outgoing_address", and this is
not perfect...).
Or maybe add this to FAQ -- i.e. "people, set up your tcp/ip
stack properly for this!" -- this particular question, I guess,
can be "cured" trivially (or not-so-trivially if there is
unusual setup here) by setting up correctly tcp routing tables
etc. Especially if this is linux, where one can tell kernel
what source address should be used by what routing table entry
(don't know if such ability exists on other systems).

Denis Shaposhnikov wrote:
>
> My situation. I have interface with ip address and one
> alias. Postfix's smtpd must receive mail for all ip addresses. But
> postfix's smtp client must use only alias's ip address (not
> INADDR_ANY) as source address. How can I do this?

Currently postfix can't use specific address for outbound connections,
it always uses INADDR_ANY (as you seen), and lefts this choice to
system's tcp/ip stack. And, as I can see, most problems around statically
assingnig source address exists on inproperly configured (or buggy) tcp/ip.
One example of this was my own setup (that is cured now) -- old solaris
(maybe 2.4, don't remember for now) sometimes incorrectly chooses src
address for default route. I have one NIC, that have two addresses --
192.168.xx.xx for internal net and 212.158.168.xx for internet access,
with default routing to 212.158.168.yy. And sometimes it tried to use
it's 192.168.xx.xx for outbound connection to outside world, and vice
versa (212.158.168.xx for internal network), especially after
"hot-changing" addresses. And now, in 2.6, this works just fine.