[Mailman-Users] cause of bounces

[Dimitri Maziuk]

On 2017-10-17 19:09, Grant Taylor via Mailman-Users wrote:

> If DKIM signature fails, then there is something wrong with the message, 
> and treat it suspiciously.  Read:  I increment the spam score.  (If the 
> spam score is high enough I reject the message at SMTP time.)
> 
> If there is no DKIM signature, I continue processing normally.

Then you seem to misunderstand what crypto signatures actually do.

If signature check fails, then the message is not what its author 
actually wrote. IRL it's mainly SorceForge and the like injecting its 
ads into signed parts, (and the real reason google is pushing https and 
dkim so hard is it's messing with their ad revenue,) but in principle if 
the check fails the message *content* is *invalid*. Whoever the author 
and whatever the content.

Dimitri