The process of bringing any email setup to Google Apps for business, is to first of all setup a new account in Google apps using the domain name of the client
Then as a part of the setup process, Google will provide you with a list of server names for which there will be a need to setup MX records in the DNS zone of the domain
These will replace any existing MX records.
Prior to doing this, there will be a need for creating all the required mailboxes on Google beforehand, so that there is no loss of emails in transition period of moving from old to new email system
Then before changing the MX records, you need to liaise with the client to make them aware of the fact that there may be a period of about a few hours when the emails sent to them may get bounced, so they should advice on the best time on changing the MX to cause least down time to them
Also, there will be a need to download the Google app sync utility to configure these new Google mailboxes on their outlook Read More