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Reduce the amount of spam for @debian.org (Was: Greylisting for @debian.org email, please)

[Santiago Vila]
> For example, we could use greylisting. Or we could reject messages that
> are known to come directly from trojanized windows machines acting as
> open proxies. Or even better, we could do both things.

Or a completely different option. Here at the university the
postmasters implemented a system to delay delivery based on blacklist
entries.  The delaying is done during the first connect, and does not
require the MTA in the other end to reconnect, like greylisting.  The
idea is simple:

 - Keep/use a list of good and not soo good blacklists for MTA hosts.

 - If the other side is listed in one of this blacklists, act as a
   _very_ slow SMTP server.  The initial hello reply is delayed 1-2
   minutes in this case, and if the client try to send anything in
   this period, the connection is dropped.  The SMTP protocol specifies
   that the client should not send anything before receiving the intro
   line from the other end, so this is safe to do.

 - This reduced the amount of spam with more than 90 percent, I've
   been told.  The current spam software do not seem to have time to
   wait for a reply, or give up the delivery after a few seconds
   without any reply.  In either case, all standard-compliant MTAs are
   able to get their mails through, even if they are listed in a

 - MTAs not listed in a blacklist is passed throught without any

Could this be an idea for Debian as well?

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