You have the means to easily communicate with your customers through email & send promotional emails/coupons etc.. You can sync your customer data to your MailChimp account & send beautiful marketing emails using MailChimp. MailChimp offers free email marketing service for up to 2,000 contacts.
Login to your Restaurant Admin, click "My Customers" then "Email Marketing" sub link.
Enter your MailChimp API Key and List ID. If you don't know how to get these, please click on the 2 links (at the bottom of this page) to see how to get them. Once you enter them in the fields below, click "Save" first before clicking "Sync/Export to MailChimp"
If you don't have existing MailChimp account, you can sign up to get started.
Video to help you find your MailChimp API key: http://kb.mailchimp.com/article/where-can-i-find-my-api-key#API
Video to help you find the List ID: http://kb.mailchimp.com/article/how-can-i-find-my-list-id/