One of our clients have SBS2003 R2 SP2. ActiveSync stopped working suddenly. OWA, OMA and Outlook are working fine. The EventLog is full of Event ID 3005
Unexpected Exchange mailbox Server error: Server: [mail.abc.local] User: [email@example.com] HTTP status code: . Verify that the Exchange mailbox Server is working correctly.
I followed everything mentioned in the following KBs with no luck since that all the settings are exactly as mentioned in the KBs
I tested ActiveSync with https://testconnectivity.microsoft.com/
and here is the ActiveSync result: