Re: reverse DNS

From: Marko Mäkelä (marko.makela_at_hut.fi)
Date: 2002-09-11 13:27:35

ruud.baltissen@abp.nl wrote:
> Sorry to bother you all but I sent an email to Marko at three different
> addresses for some days and all were returned with the following message:

The administrators of our university network have tightened the 
configuration of the mail servers in order to better block unsolicited 
messages.

>     (reason: 550 5.7.1 <marko.makela@hut.fi>... We don't accept connections
> from unresolvable addresses. Fix your reverse DNS for XXX.XXX.XXX.XXX, or
> use your ISP server.)

It would be easier to trouble-shoot this if you disclosed the address. 
For now, let us denote the numerical IPv4 address with A.B.C.D.  The 
error message specifically means that the name D.C.B.A.in-addr.arpa 
cannot be resolved.  If the address refers to a computer that is 
maintained by you, you should change its configuration in such a way 
that it does not directly try to initiate SMTP connections to outside 
hosts; instead, it should use send the messages to the SMTP server of 
your Internet service provider (ISP) for relaying.  And that server 
should definitely have a reverse DNS entry.  In my opinion (and probably 
also in the opinion of our network administrators), all visible IP 
addresses should have reverse DNS entries.

	Marko



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