On Feb 18, 12:50pm, Bill Studenmund wrote:
} On Wed, 17 Feb 1999, Andrew Brown wrote:
} 
} > >} We should perhaps deny relaying and perhaps also accepting mail from
} > >} hosts that have no valid mx or such.
} > >
} > >     Absolutely NOT, this is completely bogus.  MX records indicate
} > >machines that are intended to receive mail, NOT one's that are
} > >intended to send mail.
} > 
} > a generic bsd4.4 config file from sendmail 8.9.3 will not openly relay
} > mail from anyone.  indeed, it will only accept mail that originates or
} > terminates locally (modulo any local forwarding rules of course).
} > 
} > it will also not accept mail from an invalid sender address, ie, the
} > domain portion after the @ must either have an mx record or an a
} > record associated with it.
} 
} I think the sharp emotions stem from the fact that some sites don't add
} the "or an a record" bit, and require mx records. Rather broken. I think
} requiring an a or an mx is fine. :-)

     Actually, I think there are two issues here.  First the machine
connecting to you to send mail should have a valid PTR record, which
points to a valid A record with its IP address.  Second, the domain
part of the return address should have a valid A or MX record.

}-- End of excerpt from Bill Studenmund