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Article: 353
From: Jeff Groves
Date: 2005-02-18 11:01:46 -0500
Subject: Re: user account fishing

Removal...........: milters-request@milter.info?subject=remove
More information..: http://www.milter.info/#Support

The person that thought up that scheme for spam protection had a very 
small box in which to think.

Jeff G.

Adam Gibson wrote:

>Removal...........: milters-request@milter.info?subject=remove
>More information..: http://www.milter.info/#Support
>I have run across a problem where a mail server was doing something 
>similar to combat spam which caused us to become deadlocked with each 
>other and not be able to send email to their domain because they blocked us.
> From what their email admin told me they apparently put some bogus 
>emails on their website for spam email harvesters to find.  The 
>anti-spam software they use waits for a mail server to try and send an 
>email to that trap email address and temporarily sets a block on that 
>sending server.  I think you can see where this is going...
>A spammer sends an email to us with a from address of a random email 
>from their harvested list which just happens to be one of the emails 
>that the company put on their website.  Milter-sender sees the from 
>address and tries to do a verification of the email address against 
>their email server.  Their email server sees the rcpt to: with the trap 
>email address and blocks our servers for awhile...  Hours later when we 
>try to resend it we get the same thing over again.
>Meanwhile any emails that we need to send to that companies domain just 
>get rejected by their server because of the spam email that is trying to 
>get sent to our domain.
>I had to manually contact their email admin to get all this straightened 
>out but eventually we both setup a whitelist to bypass the spam checks 
>for each others mail servers.
>I sure hope this is not something that will catch on because it could 
>cause major problems with milter-sender.  Has anyone else seen this type 
>of spam protection on mail server before?
>Aaron Berg wrote:
>>One idea might be to just keep a log of valid email addresses in a 
>>specified database. Then just autoblacklist ip's for some period of time 
>>after they have tried too many non-valid addresses. But it seems like 
>>this would be more work then is needed. Could the milter just parse 
>>passwd and virtusertable for valid email addresses just like sendmail 
>>does? Where there is a will there is a way.

Law of Procrastination:
        Procrastination avoids boredom; one never has
        the feeling that there is nothing important to do. 

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