Google Apps Technical Transition Guide For Business, Education, and Government - Manual (Page 40)

40 Google Apps Technical Transition Guide
• See the Message Security Administration Guide for more information on
updating your mail config.
Finalizing mail routing without standalone GMS
Now that your company is living entirely on Google Apps, you can forego split delivery
and update your domain’s MX records to route all incoming mail, both internal and
external, directly to Google Apps.
• Read Configure email delivery to learn how to update your domain’s MX
records.