[ale] Spam fighting strategies

[Jeff Lightner]

The other night in the AUUG meeting it was mentioned  by one person that
they had turned on a "read delay" in email (Postfix I think) and that
this had eliminated about 80% of the spam because the bots would
disconnect.   

Unfortunately I didn't have a chance to follow up then but mentioned it
to our Exchange admin because they've been fighting an increase seen
recently in connection attempts.  It sounds as if Exchange can't do this
natively.

I'm wondering if anyone has done this on Postfix/Sendmail or some other
OSS MTA and would be willing to provide details?   

My coworker found something called "Greeting Delay" that sounds like
what I heard as "Read Delay" so it may be this but apparently that has a
problem with people that do call back to check whether email is coming
from a valid site.

Also he found doing bogus MX records in DNS - the idea being you put
your first and final MX records to dead IPs as most spam bots only check
the first or final and not the intervening real ones.   Has anyone tried
this and if so what results did you have?

Essentially we're looking at putting in a Linux server as if it were an
SMTP gateway to the Exchange server which will continue to be the
primary mail server for the company.   Any other ideas (other than
getting rid of Exchange which won't happen) would be appreciated.
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