If you'd like to tone down the volume of email notifications that your Contractors are getting, you can easily do this by accessing their profile.

Go to 'People' and then 'Contractors' from your side menu. Once there, select the Contractor you'd like to amend notifications for. Click into the 'Notifications' tab:

You'll be able to set which notifications are sent and when from here. Please don't turn off all of the notifications - it's good for them to receive at least one email per week. Notifications can be changed on a per Contractor basis and they are also able to change their notifications when they log in and go to their profile. 

Further down the page, you can also amend other notifications that the contractor is set to receive: