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List:       qmail
Subject:    RE: Question about Qmail relating to MX retry processing
From:       "Maintenance Fees Inquiries" <MaintenanceFeesInquiries () USPTO ! GOV>
Date:       2006-11-28 5:35:00
Message-ID: B9013A895FE86E47842CB2B9A07E5F13043E0907 () EXCHANGE1 ! uspto ! gov
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Dear Marc Perkel,                                                                                                           Thank you for contacting the Maintenance Fee Branch.  You should receive a response within 2-3 business days.  The tracking number for your inquiry is X200611287188.                                                                                                                                                          Maintenance Fee Branch (571) 272-6500



-----Original Message-----
From: Marc Perkel [mailto:marc@perkel.com]
Sent: Tuesday, November 28, 2006 00:33 AM
To: Uncle George
Cc: qmail@list.cr.yp.to
Subject: Re: Question about Qmail relating to MX retry processing



Uncle George wrote:
>
>> I'm not sure that's the case. It just means the those who use qmail 
>> AND (have bad reverse lookup OR are on a dynamic IP address) will not 
>> be able to send email to my domains UNLESS I whitelist their host.
>>
> I guess i'm at a loss here. Exactly how would trying each MX record in 
> turn prevent your filtering techniques from processing reverse 
> lookups, or  dynamic ip's.
>
> but the guy is correct. qmail is owned by one person, and is not 
> likely to change.  The followers of qmail,  I think, would have 
> adopted such a MX strategy, if it was *exactly*  spec'd that way into 
> one of their mandatory patches.
>

I process about 4 million messages a day. As you know graylisting is a 
popular spam fighting technique and gets rid of spam using 4xx errors 
and counts on the fact that spam zombies don't retry. But greylisting 
has its drawbacks like delaying good email. So I don't use it.

What I do instead is sort of selective graylisting targeting dynamic IPs 
and bad RDNS. But instead of delaying them for a long time with 
graylisting I only use the tem error on the lowest IP and accept it on 
the next highest IP. And this works for all MTAs except qmail that will 
keep trying the lowest MX till it times out.

But - it only happens to qmail users with dynamic IPs or bad RDNS. And I 
can add IPs to a braiddead hosts list to bypass it if someone complains.





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