Does anyone knows how the POA knows which gwsync server to notify when user receives e-mail?

I've a weird problem here. I've setup gwsync server on DMZ and we can
send e-mails from mobile devices (Ipad) to GroupWise via gwsync but the only way we can recieve e-mail from Groupwise is by configuring polling (every couple of minutes) on groupwise connector. Basically when new email arrives, the POA don't send event notification to gwsync server (access to port 4500 open on firewall).

We have another test server which is not on DMZ and it works fine...

Doing packet trace on POA I can see the packets going out
to test gwsync server on destination port 4500 but there no packets listed for gwsync server located on the DMZ....