Hi Faris,
thanks for the reply. I noticed that plesk cant control the rDNS, therefore I tried to change it through the root settings myself. I have a root server at strato so no problem with that.
I am running my own DNS through plesk for the domains on the second IP address (and that works...
second IP rDNS problems
I have exactly the same issue - I already added a second hostname to my etc/hosts for the second IP address, which works nice if I nslookup on my own servers, however it does not resolve for a normal nslookup. Probably I have to wait another 6 days until the TTL expires...