[Mailman-Users] cause of bounces

Grant Taylor gtaylor at tnetconsulting.net
Tue Oct 17 19:46:14 EDT 2017

On 10/17/2017 03:54 PM, Mark Sapiro wrote:
> What I mean is as I posted previously
> <https://mail.python.org/pipermail/mailman-users/2017-October/082611.html>, 
> RFC 5322 says the From: contains the "the mailbox(es) of the person(s) 
> or system(s) responsible for the writing of the message." and munging 
> the From: to the list address is not compliant with this requirement.

ACK  That's what I figured you were talking about, but figured I ask 
instead of assuming.

(Long pause to pontificate and research.)

I decided to see if there was an update to RFC 5322, and lo and behold 
there is.  RFC 6854, which specifically updates RFC 5322 section 3.6.2 
and allows group address syntax exists.

TL;DR:  From: can now contain a Group address / name, which can zero or 
one or more mailbox addresses.

I feel like RFC 6854 provides some light at the end of the tunnel and 
allows mailing list managers to modify the From: to be the group, 
including the Group's address.

Sender: is not needed because it would be the same as the Group's from 

Similarly, I found wording in RFC 5322 that indicates that a user agent 
forwarding a message, is actually a new message.  Section 3.6.6 has the 
following copy:

> 	Note: Reintroducing a message into the transport system and using 
> resent fields is a different operation from "forwarding". 
>  "Forwarding" has two meanings: One sense of forwarding is that a 
> mail reading program can be told by a user to forward a copy of a 
> message to another person, making the forwarded message the body 
> of the new message.  A forwarded message in this sense does not 
> appear to have come from the original sender, but is an entirely 
> new message from the forwarder of the message.  Forwarding may 
> also mean that a mail transport program gets a message and 
> forwards it on to a different destination for final delivery. 
>  Resent header fields are not intended for use with either type of 
> forwarding.

I consider a mailing list manager to be a fancy MUA that automatically 
forwards in this context.

I know that this copy is addressing the Recent-* headers, but I think 
that it clearly describes that a forwarded message (like an MLM 
generates) is a new message, and as such should reflect the person ~> 
entity (read: MLM) that is sending the new message.

> In the spirit of DMARC mitigation, we all agree that it is a necessary 
> evil, at least in some cases, but that doesn't change the fact that it 
> is an 'evil'.

I will concede that modifying the From: header is a questionable 
technique.  -  However I think it is done with a white hat spirit. 
Further, I feel like RFC 6854 helps enable (if not indirectly condone) 
use of said technique.

Grant. . . .
unix || die

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