Is this issue only intenal or external too? Have you published OWA externally? Are all your Exch servers on the same SP and RU? See this 1st - http://blogs.technet.com/b/exchange/archive/2007/09/10/3403885.aspxSukh

Hi, First please try to keep all the CAS servers in the same version with same update. You may need to patch sp3+ru3 for those internet faced CAS servers. Xiu

Installed a new Ex2007 SP3/RU4 in Site B. 15 mailboxes hosted which cannot access OWA using our regular link https://webmail.domain.com When they logon using the exchange servers FQDN it works just fine. Our Internet Facing 2 CAServers are running SP2 with RU8 in the headoffice. I think this could be the issue in our case. I have copied the \ClientAccess\owa\8.x.x.x.x folder from our new exchange from Site B to one of my CAS in the headoffice facing the Internet, manually. And then I try to logon using the FQDN of that internet facing CAS but still no go ... it gives me this err message .... Outlook Web Access is not currently available for the user mailbox that you are trying to access. If the problem continues, contact technical support for your organization and tell them the following: The Microsoft Exchange Client Access server that is proxying the Outlook Web Access requests is running an older version of Microsoft Exchange than the Client Access server in the mailbox Active Directory site. Advise Please. Thanks Much!

Is this issue only intenal or external too? Have you published OWA externally? Are all your Exch servers on the same SP and RU? See this 1st - http://blogs.technet.com/b/exchange/archive/2007/09/10/3403885.aspxSukh

Hi, First please try to keep all the CAS servers in the same version with same update. You may need to patch sp3+ru3 for those internet faced CAS servers. Xiu