Problem: Students and staff members are unable to access personal GMail while being filtered through Securly; or, you would like to prevent users from gaining access to personal GMail or other Google Apps domains.
Solution: Securly has a feature called "Restrict Google Login". It can be found in the Global Settings in your Admin UI. This will also prevent access to personal Google Drive in which users could have questionable material.
Technical Details: Please keep in mind that this is a global setting and will affect everyone. When this is applied, the error message will display on their browser that says, "This service is not available."