Thank you for this information.
The setup was zeroshell (192.168) behind a NAT router with dynDNS ZZZ and the road warrior was a Windows Mobile Phone (80.80).
I was under the impression that this should work anyway because at least MS talks about this
BTW: I forgot: I’ve modified my racoon.conf template file by adding the following section:
isakmp 192.168.XXX.XXX 
isakmp_natt 192.168.XXX.XXX 
without this I do not even get the “ISAKMP-SA established” message but receive time-out messages only.