To minimise the amount of off-topic stuff, I'm going to tackle
all the responses at once.

On Jul 6, 10:24pm, David Maxwell wrote:
} On Mon, Jul 06, 1998 at 01:46:36PM -0700, John Nemeth wrote:
} > On Jul 6, 11:20am, Bill Studenmund wrote:
} > }
} > } Sorry to spam the list with this, but direct communications don't work.
} > 
} >      Then you simply don't communicate with them.  Personally, I have
} > no time for people who's mailers are in violation of the RFC's;
} > especially, if it is a misguided attempt to block spam.
} 
} ROTFL. I can see the reply to this one coming when Greg gets in....
} 
} Greg is the primary maintainer for smail, and he is particularly fussy about
} following the RFCs strictly. 

     Ask me how much I care.

} I expect the response to be something like:
} 
} The RFCs specifically state that an MTA MUST NOT accept a message unless
} it can guarantee being able to return error messages. By using a From: address

     Really?!?  Would you care to quote the RFC in question and the
passage within it.  It is impossible to positively ascertain the
deliverability status of a message without actually trying to deliver
it.  Since there is no way to guarantee being able to return error
messages, then any RFC that said this would be wrong.  Not to mention
that even if you could deliver a message at time t, there's nothing to
say that the account won't be deleted at time t+1, so that when you
try to deliver an error report at time t+2, it will be undeliverable.

} with a host portion which has no MX, the mailer cannot be assured of its 
} ability to return errors.

     MX records are not required, an A record is sufficient.
Furthermore, the existence of an MX record does not guarantee the
ability to return errors.

} P.S. The world would contain a lot less spam if everyone configured their
} DNS fully/properly and required things like this.

     This is one of the funniest things I've heard in a long time.

}-- End of excerpt from David Maxwell

On Jul 6,  8:41pm, seebs@plethora.net wrote:
} 
} I was under the impression that the official behavior was to use the A record
} as an MX if there isn't an MX listed.

     Yes.

}-- End of excerpt from seebs@plethora.net

On Jul 6,  9:18pm, Jay Maynard wrote:
} 
} I really hate to be like this...
} ...but if a host has an A record, then isn't an MTA connected to by that
} host guaranteed to be one to which errors can be returned?

     No.  Errors that aren't discovered during the SMTP transaction
are to be sent to the envelope return address (which is sent during
the SMTP transaction).  This address could specify a different host
entirely, which may or may not have an MX record that could further
redirect the error return.

} productive than adding an otherwise spurious requirement that every host
} capable of sending mail be covered not only by an A record (which implies an
} associated PTR record), but an MX record as well.

     There is no requirement that a host capable of sending mail have
an MX record.  An MX record specifies where mail is to be sent, and
has nothing to do with the location from where it originates.  Using
it as an indication of a valid origination location is just plain
wrong, broken, and a bastardisation of the DNS system.

} > P.S. The world would contain a lot less spam if everyone configured their
} > DNS fully/properly and required things like this.
} 
} This is the first I've ever heard of an MX record being other than purely an
} optional way of collecting incoming mail on one machine for processing. I

     This whole debate went around on the spamtools list a little
while ago.  It is nothing but a misguided attempt to block spam.  The
problem is that there is nothing wrong with sending mail from a host
that doesn't have an MX record pointing to it; therefore this method
can't distinguish between spam and non-spam, and is going to have a
very high false hitrate.  Anybody that implements this method deserves
to have all their mail routed to /dev/null.

}-- End of excerpt from Jay Maynard

On Jul 6,  6:07pm, david@fundy.ca wrote:
}
} Entertainingly enough, while replying to your message I got this error
} because you don't have MX records for your host. I'm entering this manually

     MX records aren't required, but in any event...

}-- End of excerpt from david@fundy.ca

Script started on Mon Jul  6 19:35:26 1998
% nslookup
Default Server:  [199.60.222.2]
Address:  199.60.222.2

> set qt=mx
> cue.bc.ca
Server:  [199.60.222.2]
Address:  199.60.222.2

cue.bc.ca	preference = 10, mail exchanger = news.access.victoria.bc.ca
cue.bc.ca	preference = 5, mail exchanger = cue.bc.ca
news.access.victoria.bc.ca	inet address = 204.174.230.2
cue.bc.ca	inet address = 199.60.222.200
ns.freenet.victoria.bc.ca	inet address = 199.60.222.2
ccins.camosun.bc.ca	inet address = 204.174.56.1
> % exit
% 
script done on Mon Jul  6 19:35:50 1998