[Mailman-Users] Help: PTR record and ISP blocking...

John W. Baxter jwblist at olympus.net
Sat Nov 20 22:42:15 CET 2004

On 11/19/2004 20:31, "Rodd Ahrenstorff" <rodd at ahrenstorff.us> wrote:

> Could the other ISP be attempting to verify my actual server host name
> against the existing PTR record before accepting email?

Yes, they could be.

Forward and reverse lookups really should match.  (Whether to reject based
on a non-match is a policy issue over which there are endless arguments
which don't matter to you...what matters is the end result...a block.)

The MTA we use here doesn't log the sending host's name unless, among all
the names it gets back from a reverse lookup there is at least one name
which contains among its list of IP addresses a match to the actual IP
address used.  (That's the logging...accept or reject is a matter of policy
which is easily configured in that MTA thanks to a variable it makes
available.  We accept, but allow individual users to block mail from servers
with no reverse name at all.)


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