Hello,we have an problem with our exchange server. we can't use the owa and oma functionality anymore. we use an FE/BE structure in our environment and before we reboot the backend server it functs fine. we will start at the FE Server to browse the following site http://mailboxserver/oma but we become the following error mesage: Unable to connect to your mailbox on server mailboxserver. Please try again later. If the problem persists contact your administrator. also it will be an entry in the eventviewer: Request from user user resulted in the Microsoft(R) Exchange back-end server mailboxserver returning an HTTP error with status code 503 Response: Connection: close Date: Fri, 23 Jan 2009 07:48:45 GMT Server: Microsoft-IIS/6.0 X-Powered-By: ASP.NET Content-Type: text/html Content-Length: 151 MS-WebStorage: 6.5.7638 Original Request: Content-Type: text/xml Depth: 0 Content-Length: 389 Expect: 100-continue Connection: Keep-Alive Host: mailboxserver when we will start to browse the /exchange directory an the BE server we will become the following error message: HTTP/1.1 503 Service Unavailable But without an entry at the eventviewer.I hope you can help me.the followingi see, when i will change the settings at the exchange virtual directory in the application pool at the BE.I removed the davex.dll from the application pool configuration and when i will browse the site /exchange, than i will see all mailboxes as an list.i can browse between the list and use the mailbox.But when i put the davex.dll into the application pool configuration i will become the same error like: service unavailable.Best regards, Mario.

Hi, This might help: http://support.microsoft.com/default.aspx?scid=kb;en-us;305030 Leif

Hi, Please check whether the below articles can help you fix out this issue. http://support.microsoft.com/?id=823159http://support.microsoft.com/?id=837285 Thanks Allen