[oclug] SendMail as a restricted mail relay

[Dave O'Neill]

On Tue, Nov 02, 2004 at 09:32:44PM -0500, Michael P. Soulier wrote:
> 
> Greylisting may have a little more effect, but I suspect that spammers
> are adapting to it quite quickly. 

Spammers are getting smarter, but greylisting still works pretty well,
especially against spam sent from distributed "zombie networks" of
compromised machines.

There are a few problems with greylisting -- for example, if you're
greylisting before the end of the SMTP DATA command, some broken
commercial MTAs (used by legitimate senders) assume that the temporary
failure is really a permament failure and give up.  There's also the
annoyance (maybe just to you, or maybe to your thousands of customers)
of having incoming mail delayed due to greylisting.  Many people assume
email is supposed to be instantaneous, and even a 5 minute delay can
cause panicky phone calls to the helpdesk.

Would anyone be interested in a talk on server-side spam filtering, or
perhaps just on SMTP in general?

Cheers,
Dave