[Dshield] DNS MX record block question

Johannes Ullrich jullrich at euclidian.com
Sun Sep 7 20:17:04 GMT 2003

The "MX record" part of this disucssion was ok. But it got a bit of
track into the overall "what is spam" territory.

So a few opinions about MX records, spam and filtering:

(*) Every domain that is used as part of a 'From:' address,
    should have a valid MX record. Otherwise, nobody would
    be able to respond. 

(*) The machine sending the e-mail does not have to be a 
    MX record for any domain. It is fine for the reply to 
    take a different path

(*) An ISP which does not permit outbound SMTP connections
    has to provide an SMTP relay server to its clients.

(*) Nobody is under any obligation to read any e-mail and
    people may filter "at will". Some of these filters may 
    make more sense then others. This is of course more
    difficult if others (e.g. ISP) are making the decision 
    for you.

(*) There is no fundamental agreement on how to define
    spam. In particular if you had a prior business relation
    ship with the sender, or if the unsolicited e-mail was
    written by a person, it usually doesn't qualify as spam
    for some people, but it does for others.

Johannes Ullrich                     jullrich at euclidian.com
pgp key: http://johannes.homepc.org/PGPKEYS
   "We regret to inform you that we do not enable any of the 
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