Do Not Email List
You can set up users to not receive emails from the website at all. Using the Do Not Email List tool, simply enter the user's email address, and the system will no longer send any emails to that address.
Keep in mind that this sends *no* emails to the user, including things like Cart Receipts and Password Reset emails.
You must be a SuperAdmin to access this feature.
Select Do Not Email List from Admin > Users > Do Not Email List
Click Add New Record and Enter the Email Address to Block Outgoing Emails to the Address.