Re: greylisting anyone?

[Roy Bixler <rcb@ucp.uchicago.edu>]

On Thu, Feb 26, 2004 at 07:48:18AM -0700, James MacKinnon wrote:
> greylisting ( http://projects.puremagic.com/greylisting/ )
> appears to be very successful and is catching on. Our main campus
> sendmail MTA has implemented it with great results.
> 
> I recently decided to integrate it to our older departmental zmailer 
> (2.99.55) as an add-on hack to my content-policy routine and have seen a 
> very noticable drop in spam deliverables.
> 
> Sample smtpserver log entry showing the block:
> 
> ZObk13425r      DATA
> ZObk13425w      354 Start mail input; end with <CRLF>.<CRLF>
> ZObk13425#      policyprogram said: -1 451 4.7.1 Temporary greylist delay
> ZObk13425#      Content-policy analysis ordered message rejection. 
>                 (code=-1); msg='451 4.7.1 Temporary greylist delay'
> ZObk13425w      451 4.7.1 Temporary greylist delay
> ZObk13425r      QUIT

Another place to look for greylisting information is DCC --
Distributed Checksum ClearingHouse at
"http://www.rhyolite.com/anti-spam/dcc/".  They have recently added
support for greylisting to their Sendmail Milter module.  From what I
understand, it works very well at deflecting spam.  It does have a
slight downside in that there are some broken SMTP client
implementations that do not recognise a 4xx error code as being a
temporary error and bounce mail when presented with one.

-- 
Roy Bixler <rcb@ucp.uchicago.edu>
The University of Chicago Press
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