Subject: Re: Greg Woods - please fix your mailer!
To: NetBSD-current Discussion List <current-users@NetBSD.ORG>
From: John Nemeth <>
List: current-users
Date: 07/06/1998 21:04:18
On Jul 7, 12:02am, Greg A. Woods wrote:
} [ On Mon, July 6, 1998 at 20:39:53 (-0700), Bill Studenmund wrote: ]
} > Subject: Re: Greg Woods - please fix your mailer! 
} >
} > Why? Why do I have to have two entries (MX and A) for a host, if that host
} > is perfectly capable of receiving its own mail?
} Because a "host" is far more than a mailer alone, and a mailer is but
} one service a host might offer, but may not offer.  MXs point at hosts,
} mail is delivered via MXs.

    This is gibberish, and doesn't answer his question.  The answer is
that there is no need to have two entries.

} > I like the idea of verifying the DNS entry for a host, but why reject the
} > case when you get no MX and an A? You are in a position to send back an
} > error message (well, as good a position as you are with an MX record). ??
} A tremendously large number of A RRs in the DNS point at dial-up hosts

     Yeah, so.

} which do not (and cannot, by definition, if they are dynamically
} assigned) run SMTP servers.  If an SMTP client were to use such an A RR

     This statement is completely false.  There is absolutely nothing
to stop a dial-up host from running an SMTP server.  However, they
either have to have a static address (some very large ISP's only give
out static addresses), or use some form of dynamic IP, if they expect
to have reliable mail reception.

} in their SMTP sender envelope address to any receiving SMTP other than
} their own locally authorized outgoing SMTP relay gateway, then it will
} be impossible to return any mail to them.  At least with a valid MX

     Really?!?  I suggest you check out and, which
are just two organisations that offer dynamic IP addresses.
Furthmore, IPv6, which is just arround the corner, officially endorses
dynamic IP addresses.  Also check out, which is the largest
ISP in Europe, they only give out static addresses.

} there's a far better chance that the assumption a connection to the SMTP
} port at the destination MX host will succeed.

     This assumption is pure nonsense, IMHO.

} In the bigger picture there's also the fact that if your sender address
} is not pointing at a domain with a valid MX then there's a very good
} chance that your Reply-To: header (or lacking one the From: header)
} doesn't point at a domain with a valid MX either.  Anyone not using an

     This is utter nonsense.  There is no relation between header
addresses and envelope addresses.

} e-mail address with a valid MX address is either bogus, or living in the
} wrong decade.

     You forgot an "IMHO" again.  Obviously, I completely disagree
with you and so does that vast majority of the net.

}-- End of excerpt from Greg A. Woods