Recently our phones stopped connecting to the Exchange server (2003 SP2). The Application Event Log is jam packed with Event ID 3005 messages [Unexpected Exchange mailbox server error: Server: [%1] User: [%2] HTTP Status code [501] Verify that exchange mailbox server is working correctly. OWA works fine. Outlook email on clients works fine. Only phones cannot connect to the server to get mail. They can connect to setup account initially. When you try to get mail from iphone it says "cannot get mail, the connection to the server failed." When I try domain/oma I get: " A System error has occurred while processing your request. Please try again. If the problem persists, contact your administrator." When I use the remote connectivity analyzer I get: Attempting the FolderSync command on the Exchange ActiveSync session. The test of the FolderSync command failed. <label for="testSelectWizard_ctl12_ctl06_ctl05_ctl01_tmmArrow">Tell me more about this issue and how to resolve it</label> Additional Details Exchange ActiveSync returned an HTTP 500 response. and Analyzing the certificate chains for compatability problems with Windows Phone devices. Potential compatibility problems were identified with some versions of Windows Phone.

Primary reason for the OMA error is that the netframework version is wrong somewhere. It should be 1.1 and not 2.0 for all of the Exchange directories. Check through IIS manager. Simon.Simon Butler, Exchange MVP Blog | Exchange Resources | In the UK? Hire Me.

Well, after a week of struggling with this we finally have a resolution. We created an exchange-oma virtual directory and set the authentication to Integrated and Basic. We also had port 80 opened on the Firewall for Inbound Traffic to our email server static IP. I cannot explain how port 80 got disabled on our firewall or what happened to the virtual directory, but email is flowing to all phones now.