If there are volunteer's who no longer wish to receive swap request emails, you as the administrator can disable these emails from their profile:
1) In the Volunteers pane, edit the volunteer's profile by clicking on their name and using the "Edit Volunteer" button on the right.
2) From the Edit Profile window, click on the arrow to the right of their email address and click on where it is checked and says, "Send swap request emails." This will un-check the option and turn off swap requests for that volunteer.
A volunteer may also log in to the Web Terminal and from the My Profile tab, indicate themselves they no longer wish to receive swap requests.