3.2.5.3 Sending a RopSpoolerLockMessage ROP Request
The client sends a RopSpoolerLockMessage ROP request ([MS-OXCROPS] section 2.2.7.5) after determining, through an implementation-dependent mechanism, that it can handle the message.<11>
After a client makes a successful request to mark the message as locked, it MUST subsequently make a request to mark the message as unlocked or finished.