Re: 7. BCP - Mail Administrators: Checking HELO (was: [Asrg] 0. General - Administrative - for M. Wild)

[Steven F Siirila <sfs@tc.umn.edu>]

On Sun, Aug 31, 2003 at 03:49:24AM +0200, Brad Knowles wrote:
> At 8:04 PM -0500 2003/08/30, Steven F Siirila wrote:
> 
> > We have seen about 1,200,000 different IP addresses connecting to us in 
> > the
> > past six months and we block about 1,000,000 SMTP connections on our MX
> > servers every week on average.  What other stats would be of interest?
> 
> 	What's your breakdown of why those connections are blocked?  How 
> many unique blocks are due to which blacklist?  How many unique 
> blocks are from lack of rDNS?  How many unique blocks are there by 
> domain-based blacklist?  How many unique blocks are there due to 
> other techniques?

I will try to post some data soon.

> 	I assume that once you have a positive response on one of those 
> checks, you reject the connection and you don't bother trying the 
> other checks as well.  Could you re-process your data to apply all 
> checks to all IP address/envelope sender/recipient combinations, to 
> see where certain blocks might overlap?

No, we reject on potentially multiple reasons.  Dynamic IP, no rDNS when
rDNS is required, known spammer, known open proxy, known open relay, etc.

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