[Mailman-Users] cause of bounces

Grant Taylor gtaylor at tnetconsulting.net
Fri Oct 20 00:26:25 EDT 2017

On 10/19/2017 12:37 AM, Stephen J. Turnbull wrote:
> The IETF has NO position on WHEN this should be done because it's not 
> relevant to interoperability.  My personal reasoning with respect to 
> mailing list managers like Mailman which normally pass through all 
> text/plain, and perhaps add some tags to Subject and prefix or suffix 
> the body, is that users (including posters) would be quite annoyed if 
> de-duping didn't work.  And those of us who deal with mail in 
> sophisticated ways would be quite upset if the Message-ID we give it 
> doesn't correspond to the Message-ID distributed by the list and in 
> the archive.

I believe RFC 6377 makes it fairly clear if a message is new or not. 
TL;DR:  If anything other than the SMTP envelope is modified, then the 
MLM is a resending MLM, which necessitates a new message with a new 
author and Message-ID.

I can respect your concern about the Message-ID changing, especially 
with deduplication.  However, I counter that the new message from the 
resending MLM is in fact a different message than the one that the 
original author sent to the resending MLM.  So, if you were in the To / 
CC / BCC of the message from the original author, you /should/ receive 
two copies of the message.

Fortunately nicer MLMs, like Mailman, can detect that a list subscriber 
was included in the To or CC and act on the subscriber's configured 
option if they want to receive a copy of the message from the MLM that 
they received directly.

Grant. . . .
unix || die

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