Using your existing business email addresses, the only difference you and your customers will notice is how much more efficient you and your team have become.
Efficient labeling of emails (imagine Post-It notes stuck to a piece of paper) means that they can be filed using a system that suits you. Use Google Search to find exactly what you were looking for using the broadest of terms. Accessible from any computer with an internet connection and have email delivered to your phone with Blackberry rivaling speed.
Never concern yourself with having to delete an email because you will have a mailbox 50 times larger than the industry average.
Best of all, Gmail for business integrates with Google Calendar and your team can continue using MS Outlook.