Outlook Web Access problem(OWA)

Hello,
WE currently have existing OWA which is composed of one hostdomain (domain_master)and 2 backup domains and this are working fine.
Today i created another exhange server for our site which is a PDC and i connect it to our host exhange domain(domain_master) via X400 and site connector and it's working great except for OWA.
Now the problem is why is that i couldn't check mailbox on my newly created exchange.

Do i need to:
1. install OWA also on the new exhange pdc.
2. install iis 4.0 on the new exhange pdc.

or is it because they have different domain names.

Thanks and i'll wait for responses