18.104.22.168 Sending the RopBackoff ROP Response
If the server version, as defined in [MS-OXCRPC] section 22.214.171.124.3.2. is greater than 08.00.0525.0 and the client version, as defined in [MS-OXCRPC] section 126.96.36.199.3.2, is greater than 12.0.4228.0, the server SHOULD substitute a RopBackoff ROP response in place of the response for the delayed ROP request. If either the client or the server is an earlier version, then the server MUST instead fail the RPC by raising the RPC_S_SERVER_TOO_BUSY exception, as specified in [MS-OXCRPC] section 188.8.131.52.
If ROPs are specified in a RopBackoff ROP response, all subsequent ROP requests SHOULD NOT be processed.
If MAPI extensions to HTTP<23> are used, The RPC_S_SERVER_TOO_BUSY exception is raised. It includes an HTTP status code of 200 and a response code of 0 (success). A MapiHttp status code, a DWORD with a value of 0x6BB, immediately follows the response code.