Restrict sending host for some (but not all) recipient addresses?

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Restrict sending host for some (but not all) re...
\ Rich Wales (13 Jun 2007)
. \ mouss (13 Jun 2007)

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Subject:	Restrict sending host for some (but not all) recipient addresses?
Group:	Postfix-users
From:	Rich Wales
Date:	13 Jun 2007

Is there any way for Postfix (2.3.8) to enforce different client access
restrictions, depending on the recipient address of an incoming message?

I have a Postfix system which is servicing two domains (one for local
delivery, the other as an MX relay). I would like to do some special
screening of incoming mail that is bound for the "local delivery" domain
-- specifically, requiring that mail addressed for local delivery must
be arriving via one of my local network's SMTP servers -- but NOT do this
particular restriction on incoming mail for the "relaying" domain.

In this particular setup, all legitimate "local delivery" mail should
be arriving on my system via one of a small set of nearby SMTP relay
hosts. If you imagine my host is named mysite.example.tld, I want ONLY
hosts in my local network (using the example.tld domain) to be able to
deliver mail directly to me at richw; everyone else
on the Internet at large must address mail to richw and have
it forwarded inbound to me via my local network's MX server(s). If any
mail from a random Internet site tries to send mail directly to my host,
I will assume it's spam and wish to block it.

HOWEVER, I only want to do the above sending-site restriction act for
mail that is to be delivered locally. If mail is addressed to someone
in the other domain -- the domain that I'm relaying to -- I want my
system to accept it from any SMTP server on the Internet.

Is there any way to do this sort of thing within a single instance of
Postfix that handles incoming mail bound for both domains? Or do I need
to run two separate SMTP servers (presumably by dual-homing my server
and using different domain names / IP addresses as MX forwarders for
each of the two domains)?

--
Rich Wales === Palo Alto, CA, USA === richw
http://www.richw.org === http://en.wikipedia.org/wiki/User:Richwales
"The difference between theory and practice is that, in theory,
theory and practice are identical -- whereas in practice, they aren't."