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Article: 1218
From: Mathias Koerber
Date: 2006-10-26 03:06:47 -0400
Subject: Re: 450 vs 451 error code for greylisting (milter-gris)

Removal...........: milters-request@milter.info?subject=remove
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--------------------------------------------------------

Quite a while back, from the archives:

> Date: 2006-Mar-27
> From: Anthony Howe 
> Subject: Re: 450 vs 451 error code for greylisting (milter-gris)
> 
> Removal...........: milters-request@milter.info?subject=remove
> More information..: http://www.milter.info/#Support
> --------------------------------------------------------
> 
> fif3 wrote:
>> I've been reading some discussions about the advantages to using a
>> 451 error code instead of 450 for greylisting and I was wondering
>> what your take is on it, and if milter-gris might be changed any
>> time soon to 451. Thanks by the way for the great work.  -s
> 
> No.
> 
> http://www.snert.org/reference/RFC-HTML/rfc2821.html#section4.2.3
> 
> A rejection response for security and/or policy reasons is a 550 code.
> 
> 	550 Requested action not taken: mailbox unavailable
> 	    (e.g., mailbox not found, no access, or command rejected
> 	    for policy reasons)
> 
> It follows then that greylisting is a temporary rejection for security 
> and/or policy reasons, for which 450 is used. With extended error codes 
> it would be:
> 
> 	450 4.7.1	temporary reject for security and policy reasons
> 	550 5.7.1	permanent reject for security and policy reasons

However, the question was 450 vs 451, not 450 vs 550...

found@ http://www.greenend.org.uk/rjk/2000/05/21/smtp-replies.html:
> 450 	Requested mail action not taken: mailbox unavailable
> 451 	Requested action aborted: local error in processing
> 452 	Requested action not taken: insufficient system storage


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