22.214.171.124 Handling HTTP OPTIONS Command Requests
The server parses HTTP OPTIONS requests from clients as specified in section 2.2.3 and formats its response as specified in section 2.2.4. The server's response MUST contain both the MS-ASProtocolCommands header, as specified in section 126.96.36.199.2.1, and the MS-ASProtocolVersions header, as specified in section 188.8.131.52.2.2. The server uses these headers to indicate which ActiveSync commands and which ActiveSync protocol versions it supports.
A protocol server can support multiple versions of the ActiveSync protocol. This specification, and any protocol specifications that cite it as a dependency, apply to the server configuration when the value of the MS-ASProtocolVersions header is set to a value that includes "16.1", "16.0", "14.1", "14.0", "12.1", "12.0", or "2.5".<11>
The latest version of the ActiveSync protocol is 16.1. Older versions are 16.0, 14.1, 14.0, 12.1, 12.0, and 2.5. Some commands and functionality described in the ActiveSync protocol documentation are not supported by all of the protocol versions. See the command and element descriptions in the ActiveSync protocol documents to determine which commands, elements, and capabilities are supported by the protocol versions.