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From: "Martin.Hepworth" <martinh@solidstatelogic.com>
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Subject: RE: greylisting with CGPro
Date: Sat, 6 Sep 2008 09:41:31 +0100
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Also the spambots are getting clever and are starting to retry, so greylisting is becoming less effective.

It's still a useful tool to have in your armoury though.

-- 
martin

-----Original Message-----
From: Mark Nipper <it@allwebleads.com>
Sent: Saturday, September 06, 2008 12:18 AM
To: CommuniGate Pro Discussions <CGatePro@mail.stalker.com>
Subject: Re: greylisting with CGPro

たまちゃん wrote:
> Mark Nipper wrote:
>> That's incorrect. Even RFC 821 (http://tools.ietf.org/html/rfc821) 
>> states that a client should retry after receiving a 400 level message. 
>> This might be ignored by much older clients of course, but there's 
>> nothing much to be done about substandard implementations.
> 
> RFC 2821 states that the SMTP client is "encouraged" to try again.

	Hence the increased level of "severity" with the encouraged instead of just saying should as it did in 821.  Essentially, to an implementor, you're really dumb if you don't follow this guideline, but hey, it's not necessarily a hard requirement.  :)

	But yeah, greylisting is going to bounce legitimate messages occasionally.  There are just too many crusty, old, broken mail systems out there still.

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