Hi, Naveed,
Yes, this feature is only available in UM 7.2 or 7.3. Please consider upgrading or installing the newer build at your earliest convenience.
I'm assuming you are running OCUM 7.1 connected to OPM. There is a way not to receive this event, but in a more complex way.
Go to Performance\Configuration\Configuration\Event Handling\System Defined Threshold Policies, and uncheck the Email alert box.
This will stop this event from being "published" and sent through email.
The caveat is it will also stop the aggregate utilization system-defined event from being sent as well.
See attached screenshot for details.
Julia