4.40.5: IPBlock 451 versus 550

Jan-Peter Koopmann Jan-Peter.Koopmann at SECEIDOS.DE
Thu Mar 17 09:14:12 GMT 2005

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On Wednesday, March 16, 2005 6:41 PM David Lee wrote:

> I note that Mirapoint (www.mirapoint.com) has a feature called
> MailHurdle which deliberately uses 4xx-like temporary failures to try
> to stall spammers.  

Unless I misunderstand something here this method is calles greylisting and is many things but new. Should be installed on the MTA however and not in MailScanner. There are many guidelines and packages for all important MTAs. It is generally very effective but has a big problem at least for commercial clients:

> By contrast, legitimate email (yes, and some residual spam) would
> always try again a few minutes later, and so when it does, this time
> the call is accepted ("I've just met you, so I accept you 200-like").

The problem is "a few minutes". Depending on how the sending MTA is setup, this can be anything. The default for many MTAs is 15 minutes, but if the Administrator chose 60 minutes etc. this means that the first message will take at least 60 minutes to be delivered. This is not acceptable for most business users I have met.


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