Options for migrating mail from Google accounts or IMAP servers
If you've created a new Google Apps account for your organization's email, you can migrate your data from your old Google account or an IMAP server, using one of the following tools:
Data migration service
The data migration service is the recommended way to migrate mail. It's clientless and cloud-based and easy to set up and monitor. You do everything in the Google Admin console.
Check the data migration service prerequisites before you begin.
Google Apps Migration for Microsoft® Exchange (GAMME)
GAMME is a utility that migrates your mail, including labels and archived mail, to your Google Apps account. GAMME can also migrate other data, but requires you to install the tool first. For details on how to migrate data using GAMME, see Use GAMME to migrate mail from Google accounts or IMAP servers.
Check the GAMME prerequisites before you begin.
Third party tools
You can also check out the Google Apps Marketplace to review migration solutions provided by third parties.