Re: [Asrg] reject and DSN, was What are the IPs

Ian Eiloart <> Thu, 02 July 2009 14:10 UTC

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Date: Thu, 02 Jul 2009 15:10:34 +0100
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Subject: Re: [Asrg] reject and DSN, was What are the IPs
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--On 2 July 2009 13:54:09 +0000 John Levine <> wrote:

> You appear to be under the impression that a sender would obtain and
> use valuable information from a DSN that can't be sent in a rejection,
> which is completely contrary to my experience.  I don't spend an
> enormous amount of time reading DSNs, but my mailing list software
> does and all it really wants to know is the address that bounced,
> which rejections reliably provide.  DSNs often give no hint what
> address the bouncing message was sent to.  That's why we have to use
> kludges like VERP.

I guess rejections are more useful for automated processes, but they're 
often converted to DSNs anyway. Certainly, our mailing list software only 
sees DSNs. VERP may be a kludge, but it is a solution.

DSNs have the potential to be more useful to humans if they're constructed 
by the MTA that has more information.  In fact, we never reject a message 
submission because most MUAs display little or nothing of the message. 
Instead, we accept all authenticated submissions, and generate a DSN if 
there's something we don't like (except unauthorised sender addresses, of 

DSNs are often hard to understand, especially when the sending MTA is 
trying to wrap an error message. All too often, they discard the error 
message and insert completely misleading diagnostics.

Ian Eiloart
IT Services, University of Sussex
01273-873148 x3148
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