Add second Exchange server to OWA

[LuTran]

Hi,

I'm adding the second Exchange server 5.5 to the existing site. The Exchange system see both existing one and new one. However, OWA does not. Users having mailbox in the second servwer cannot accees to their mailbox via OAW. The error is

OWA was unable to get to your inbox.

To try to logon again, click here.

For additional help on troubleshooting this problem, click here

Even domain admin can't access, too. Any hint ?
Thank in advance.
Long Le