On May 29,  3:45pm, Wolfgang Rupprecht wrote:
} Subject: Re: Sendmail and licensing (fwd)
} 
} John F. Woods writes:
} > Can sendmail 8.9.0 reject mail due to non-envelope headers before receiving
} > the entire message?  
} 
} Well, not really.  The headers all come over as part of the SMTP DATA
} command along with the message body.  You have to physically transfer
} the message.
} 
} On the other hand you don't have to accept the message at the SMTP
} level.  You can blow it off with a "550 stick this spam in your ear
} buddy", and the host that is sending you the spam gets to generate a
} bounce msg.  This is a very nice feature, since nothing gets the
} undivided attention of the admin of a spam-relay more quickly than
} having a bunch of bouncing spam messages from an off-site sender to
} other off-site recipients.
} 
} > It's not too hard to set up procmail filtering to nail these (I nail
} > these and a few others), but that's after inhaling the whole
} > message.  (It also requires a fork and exec, but procmail will also
} > do local delivery, so it's no worse for real mail.)
} 
} The main advantage over procmail filtering it is in the sendmail
} filtered case you get to decline the responsibility for the msg, and
} the other guy gets to send the bounce.  Its kind of heart-warming
} really. ;-)

Also, if the spam is being sent by a directly connected spam engine,
it won't bounce the message, but if you accept the message and then
try to bounce it, you'll likely send the bounce to an innocent third
party.

Some limitations of the new filtering capabilities are that you can't
filter on the message body or comments in the headers.  This doesn't
allow you to filter out spam injected by UUNET or Compu$pam dialin
ports and relayed through a third party since that information is
stuffed inside ()'s.

There's also the question of what to do about spam that has been
sent by way of a mail list that you subscribe to.  Rejecting the
mail based on the envelope is safe because it has been sanitized
by passing through the list, but if you reject the message based
on the headers or the body, you'll incur the wrath of the list
owner by bounce any spam to his mailbox.