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Re: Problems with mail system? [Fwd: Returned mail: User unknown]

On Thu, Sep 07, 2000 at 05:16:23PM -0500, Joseph Carter wrote:
> On Thu, Sep 07, 2000 at 05:37:25PM -0400, Adam McKenna wrote:
> > > My reverse DNS does not match my forward DNS.  I have @home.  Only
> > 
> > They don't need to "match".  Your IP just needs to resolve to something, and
> > that something needs to resolve back to your IP.  This has no effect on what
> > From: addresses and envelope senders you can use.
> Miquel van Smoorenburg and others seem to think that they do need to
> match.  if you connect to my IP, you will see that neither
> nor cc659474-a.indnpls1.in.home.com appear in the greeting.

So?  Anyone who asked for that would be unreasonable.  Besides, nobody's mail
server is telneting to your port 25 to see what your SMTP greeting says -- 
that would be insane.  It's a simple double-lookup.  The PTR record is
queried, and checked to see if it matches that particular A record.  Not all
MTA's even do this.

The only other check that some MTA's perform is checking that the domain in
the Mail From: header (the envelope sender) is a real domain.

To sum up, your particular problem is not with DNS, it's with some fool
arbitrarily blocking either you in particular, or some larger network which
includes you.


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