Once restaurant customers have signed up for your email communications they may need to update their information. Whether it's a new email address, or they have a new food allergy letting them update this information easily makes sure your communications are effective. Create a form where current customers can update their information. This can involve a few favorite foods, dietary restrictions, or updating contact information. Since you're already sending emails to patrons, including a link at the bottom of the email would allow them to change their preferences via the form. Once you attach the link to the bottom of the email continue to send your emails as normal.