405 Method Not Allowed: Most Exchange servers are configured to accept standard HTTP requests of type "GET" or "POST". However, the Exchange Web DAV protocol also uses other methods such as "PROPFIND", "SEARCH", or "X-MS-ENUMATTS". Those methods (also known as verbs) may be blocked by your IIS configuration.
Resolution:
If migrating from Exchange 2007, check which verbs are allowed in your IIS Exchange configuration and ensure methods listed above are allowed.