2010 OWA doesn't work in multi servers

Specs: Exchange 2010 Sp2 rollup 2 on 2008R2 Sp1, both exchange servers have CAS installed.

First Server1 installed and works fine. Both Local/Internet OWA redirects perfectly. Any mailboxes that sit on Server1 can access OWA from Local or internet

PROBLEM:

I recently Added an additional Server2

For example: Mailbox1 is on Server1 and Mailbox2 is on Server2

From Local: Mailbox1 can OWA via Server1, Mailbox2 can OWA via Server2

I can't OWA Mailbox2 via Server1 and vice sersa. It redirected me to https://webmail.server.com/owa.

From Internet:  I can't OWA Mailbox2 from external either.

Am I missing something? Thanks for your help