I am in process of migrating to Exchange 2k7 and am having an issue which will have a negative effect during the transition period.I created a test mailbox on the E2k7 box. I can connect w/ Outlook and can access via OWA on a 2k7 box. (I layer it out into three tiers: Mailbox; Hub; OWA. This is the same as we have for our E2k3 environment. We have multiple sites around the globe, but only one official domain. To do corporate branding, legal messages, etc. we have everything flow through a hub, then through the spam firewall.)I cannot connect to the E2k7 mailbox on the E2k3 OWA box however. OWA page doesn't present an authentication error, but it just sits there after login. Needless to say, ActiveSync devices don't work.Is there a way to get a E2k7 mailbox to be usable via E2k3 OWA?

HI, No you cannot access via 2003 OWA Exchange 2003 OWA doesnt support to get Exchange 2007 mailbox via it. Because Exchange 2003 front end servers doesnt supports Exchange 2007 mailboxes, But Exchange 2007 CAS servers supports Exchange 2003 Backend servers and it will allow to access exchange 2003 mailboxes via CAS server.So you cannot access exchange 2007 mailboxes via Exchange 2003 OWA. Outlook Web Access and Exchange 2007, Exchange 2003, and Exchange 2000 Coexistence------------------------------------------------------------------------------------------------------------------------------http://technet.microsoft.com/en-us/library/bb885041.aspx Regards Chinthaka

Well that's a bummer. So the procedure would be front-end then back-end, I guess. I guess it works either way.Thanks!