By using custom domain name(domain.com) to point to G Suite Mail email server in cPanel, you may refer to the step as below and change the MX record record from your cPanel.
Caution: Please do not modify the MX record if you are not sure on how to change it.
Please contact our support team shall you require further assistance.
1. Login to your cPanel account.
2. Navigate to DOMAINS.
3. Click Zone Editor.
4. Click on the +MX RECORD.
5. Add the MX record with the Priority and Destination. Below is the priority and destination of Google Apps Mail:
1 (priority) aspmx.l.google.com (Destination)
5 (priority) alt1.aspmx.l.google.com (Destination)
5 (priority) alt2.aspmx.l.google.com (Destination)
10 (priority) alt3.aspmx.l.google.com (Destination)
10 (priority) alt4.aspmx.l.google.com (Destination)
6. Now navigate to Email Routing under EMAIL.
7. Select the desired domain from Domain drop down menu. Click on Remote Mail Exchanger and click Change.
8. Kindly allow few hours for the DNS propagation.