SpamHero is an excellent solution for customers at Hostgator that want premium spam filtering. 

Here are the steps for setting up SpamHero with Hostgator:

1.  Review Hostgator's instructions for changing your MX records here:

Changing Your Hostgator MX Records

2. Using the MX records assigned by SpamHero, login to your Hostgator account and update the MX records for your domain.
3. Because Hostgator uses cPanel, it is important to follow these instructions after you make the MX record change (it has been reported that if you make these changes first, they will sometimes get reverted back to the default settings when you update your MX records):

Configuring cPanel with SpamHero

You must enable the "Local Mail Exchanger" option, otherwise Hostgator's servers will fail to recognize that they are still hosting your email.