Email Problem

[Henry Spencer]

On Fri, 21 May 2004, William Park wrote:
> It's doing reverse DNS check to see if MAIL FROM is the same as IP.

That's fairly unlikely, since there are *many* situations where the two
wouldn't match.  (Although stupid people might fail to realize this...)

More likely, I would think, is that it is looking up the IP to get a name
for that number, checking that for consistency, and finding that it fails
the test.  (Look up number, that gives you a name.  To check, look up the
name, giving you possibly several numbers, and if the original number
isn't in that list, there's trouble -- this check should *never* fail.)

Many ISPs are sloppy about providing *consistent* forward and reverse DNS
entries, especially for dialup lines.  And some anti-spam filter systems
really want a *reliable* name for the other end, to use in things like
bad-guy database lookups... so it's not surprising that it might insist on
a name that passes the consistency check. 

                                                          Henry Spencer
                                                       henry-lqW1N6Cllo0sV2N9l4h3zg at public.gmane.org


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