Mailing List Message #5841
From: Gergely Olah <>
Subject: SMTP sender verification with multihoming
Date: Fri, 28 Apr 2000 17:30:07 +0200
To: <>
X-Mailer: Claris Emailer 2.0v3, January 22, 1998
Dear all,

we have a SIMS 1.7 server with multiple domains. The host has one IP
address, and some 5-6 domains have point to that IP address. I have the
mail router set up: accounts in different domains have prefixes, like:


...anyway: receiving mail works just fine from anywhere, and all the
domains can perfectly send messages to each other.

My problem is that some servers ot there seem to do reverse-DNS lookups
on my server's IP address. The server always uses the default IP address,
the one that is set in Mac OS's TCP/IP control panel. So: if the user
sent the mail as, the recipient's SMTP server will do the
reverse-lookup, and it gets an other hostname (the one, that belongs to
the default IP address, and not the one, that is in the message, as
sender. -> So, some servers drop our messages: in the log I see errors

'From' rejected, got 451 <>... Sender domain must resolve\r

Is there a quick and dirty remedy?
Is there a way to tell SIMS to use specific secondary IP addresses, when
sending mail from peticular domains? I can add as many IP addresses to
our servers as I wish. (Well, at least, I could add as many as domains we
Does it help, if I upgrade to 1.8b?

Any comments are much appreciated.


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