[horde] lists.horde.org break S/MIME and DKIM

[A. Schulze]

Ralph Ballier:

> Meanwhile it works and I have an own mail certificate (look above in the
> header).

your message was modified on transit and the S/MIME signature is broken.
Probably because the listmanger ( mailman ) append a footer to each message.

One more reason to configure the listmanager not doing this anymore.
So again: my call for reconfiguration mailman to not modify all messages:

How?
    
https://sys4.de/en/blog/2013/08/11/dkim-konforme-mailinglisten/#mailinglisten-manager-dkim-konform
   it's on german. But as summary, add this to mm_cfg.py:

   # Do not break existing DKIM signatures
   DEFAULT_SUBJECT_PREFIX  = ""
   DEFAULT_MSG_HEADER = ""
   DEFAULT_MSG_FOOTER = ""


does it hurt?
   mostly no:

   - http://dovecot.org/list/dovecot/2014-June/096547.html
   - https://unbound.net/pipermail/unbound-users/2015-July/thread.html
   -  
https://listi.jpberlin.de/pipermail/postfixbuch-users/2015-July/063192.html

does it safe the world?
   no

   there are corner cases where mailman in older versions ( < 2.1.20 )
   but it help to keep email authentication valid most of the time.
   not working 100% is no reason to not use 95%

Andreas