Terje> 2. Dump messages where FROM <> SUBMITTER.
But an MTA can reject the message at the MTA level.
Right -- the MTA can easily look at the header as it receives the
message data and reject the message at the end of the data if it fails
the test.
While I sympathize with the goal of separating function, it's been
apparent for a long time that you often need to combine the
implementation of multiple levels to get acceptable performance. If I
had to push all my MTA spam filtering into the MUA, the load on my
mail servers would go up an order of magnitude. Even if it has to
read the whole message before rejecting it, MTA time rejection is a
lot cheaper than MUA rejection because it avoids the entire queue and
deliver process.
For that matter, since no spammer with a room temperature IQ will ever
send spam with a SUBMITTER that doesn't pass, we're going to have to
check SUBMITTER vs. From: on every message anyway, so we might as well
skip a lot of useless programming and just check the From: directly.
Regards,
John Levine, johnl(_at_)taugh(_dot_)com, Taughannock Networks, Trumansburg NY
http://www.taugh.com