[Mailman-Users] DMARC victim example?

Richard Damon Richard at Damon-Family.org
Mon Apr 14 03:48:52 CEST 2014

On 4/13/14, 9:06 PM, Peter Shute wrote:
> Richard Damon wrote:
> My guess on how this works is that when you deliver to Gmail, 
> one message will actually have many recipients, and you will 
> get just a single rejection, which will be charged to the 
> first person on the list by mailman. How they are grouped is 
> likely a function of the full subscriber database, so some 
> might get hit by a few, then someone (un)subscribes, changing 
> who will be charged with the "problem" Whoever is "first" in 
> the list of messages going to Gmail, is much less apt to be 
> moved, so the most likely to get kicked off.
> Is that true (assuming your guess is correct) of all domains where there are multiple recipients, or just gmail? And only to spam rejections, or also to disabled mailbox rejections, etc?
> Doesn't seem much point disabling accounts for bouncing if you can't be sure which one it is.
> Peter Shute
This is based on my understanding of how email works and mailman works.

When sending a large number of copies of identical emails to a single
server, you want to batch it into one message with multiple recipients
(this assumes you are not using VERP, which would cause the messages to
not be identical).

When the recipient server gets the message, it can reject the message as
a whole (which is what seems to be happening here), or it can indicate
that a particular recipient can not receive it (which would be more
common for things like mail box full or no such address).

My guess is that mailman has no code to specially handle the first case,
and when it gets a single bounce notification, assigns that bounce to
just one subscription, likely the first.

Richard Damon

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