If select volunteers do not wish to receive "Sub Request" emails, you can create that exception within VSP.  To do this, open the program, go to the Web Terminal pane and click on the "Web Terminal settings..." button.

In the new dialog that opens, click on the "Swap Requests" heading.  Find and check the "But don't send such swap accept emails to these volunteers..." option, and a list of your volunteers will appear.  Click on a volunteer to select them. Hold down the Ctrl key on your keyboard to select multiple names at once.  

Click the OK button in all dialog boxes once finished, and from that point forward those names selected will not receive email notifications regarding sub requests.