Jeroen,
Did you want the geonetwork developer list to be the default assignee of tickets, or to be always cc:ed on all geonetwork tickets?
I have set smtp_replyto = geonetwork-devel@… in /var/www/geonetwork/conf/trac.ini, and restarted apache. So that should be the reply address for future trac email.
Arnulf,
it might be best for you, or the Mapbender trac-meister to submit a new ticket for mapbender when this is done so it can be clear the configuration you want, the address to send to, etc. BTW having all trac traffic go through the developer list can produce a lot of noise in a busy project.