Google Apps Technical Transition Guide For Business, Education, and Government - Manual (Page 38)

38 Google Apps Technical Transition Guide
Now that your IT team has been living on Gmail and has had an opportunity to identify
and resolve any issues with Gmail in your environment, you can switch your mail
routing strategy from dual delivery to split delivery. With split delivery, incoming
messages are delivered either to a user’s Gmail account or to their legacy mail
account, depending on the user. This allows your IT team and early adopters to live
on Gmail exclusively, without affecting the rest of your users.
The way you set up split delivery depends on whether your Google Apps solution
includes standalone Google Message Security.
• If your Google Apps solution includes standalone Google Message Security, read
the
Message Security Administration Guide to learn how to set up split
delivery.