This article explains how to block all web mail except for a certain Google domain. Users will no longer be able to access their private Gmail accounts and can only log onto a Gmail for a custom domain.

The following sections are covered:

How to block web mail

How to block web mail

1. Navigate to Firewall
2. Click +Add Firewall rule
3. Create a firewall rule as shown below:

Note: Here we chose the pre-made web policy called No Web Mail but any web policy with the category Web E-Mail selected and set to Block will work.

Allow custom Google Domain

1. Navigate to Web > Policies.
2. Edit the policy you used in the firewall rule above.
3. Open up the Advanced Settings option at the bottom of the policy edit screen.
4. Enable Restrict login domains for Google Apps by checking the box.
5. Next to Allowed domain(s) type in the domain that is allowed to access Google Apps despite the web mail block.

 

Reference by Sophos.com