You can, within a project click the settings icon. Make sure you are under Project Settings and toggle the Online/Offline button.
This will effectively turn off all outgoing emails for the whole project until switched back Online.
Note: emails will not be queued during the time the project was offline
Notifications can also be turned off per module, note that this is a system-wide setting and not per project.
This screen is located within System Settings--->System Configuration--->Notification Settings
For help and support please contact Support