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Sender access restrictions by connecting back to the MX/A server(s)
From: Guido Van De Velde (Guido.VanDeVelde
cc.kuleuven.ac.be)
Date: Wed Oct 01 2003 - 17:31:28 CDT
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Hi,
One ISP which should accept our mails we send them, check not just the
existence of the sender domain, but also connects back to the MX or A
servers of the sender domain.
Because of our complex internal structure and firewalling policy they
cannot always reach those servers. They refuse those mails. They say
it's more secure to check if the sender address exists (including the
postmaster address of that domain).
For instance a mail from userhost where host does exist and has regular
dns A and PTR records, but its tcp/25 is protected by our firewall. I
know it should be userdomain with mx'es reacheable from Internet, but
is it up to someone else to judge on that ?
They refer to
http://sourceforge.net/docman/display_doc.php?docid=6747&group_id=1
Is this behaviour normal ? We do everything to keep out virussen and to
check on spam. We are _not_ open-relay. We only send out regular mail.
Has anyone an opinion about this ?
guido
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