Looks like someone has screwed up their spam sending programs...
This is always going to be a hard type of message to catch, because whilst it probably is spam, it's also just an error message - no actual spam content!
Even so, the best action to take it to send it on to us so that we can update our rules to block further messages - both for you and all other customers. Forward the message as an attachment to firstname.lastname@example.org, or if you're using the Outlook you can get the plug-in from the support site which gives you a "report spam" button.
I wouldn't recommend writing your own rules to block spam unless it's a very "local" issue - it's almost always going to be best to leave it up to our spam rule writers to do it for you, but obviously we need to see the message first.
We have configured the outside and inside Interface with official ipv6 adresses, set a default route on outside Interface to our router, we also have definied a rule , which also gets hits, to permit tcp from inside Interface to any6.
In Syslog I also se...