Google has a path to migrate your Exchange Server or Lotus Notes mail stores to Google Apps for Domains.
Google has released a clear pathway to migrate corporate email from Microsoft Exchange or Lotus Notes to their Google Apps for Domains service.
It uses the IMAP feature in Exchange or Notes to extract information and inject it into Google’s server Details at Google.
For small instances this could be a cost-saving move. Google Apps for Domains costs $50 per user per year for the Premier edition, free for the Standard version. A hosted Exchange Server systems costs around $120 or more per user, per year. It’s certainly cheaper than buying and maintaining your own Exchange Server machine – even in the economical Small Business Server option. However Small Business Server gives you considerably more flexibility, especially when it comes to mailbox sizes, public folders etc.