Building a data-driven approach to keeping user contacts up-to-date
Do you remember every email address you use with every one of your online accounts? You know, the accounts you use with your spam email address, versus your "real" email, versus your work email? Probably not. And neither do your users. That is why it makes sense to periodically confirm that you have the best contact information on file for your customers. You could do this every month, or once a year, or take a data driven approach that lets you focus only on the customers that will most likely find your notices to update their contact information helpful, rather than annoying.
Application logic for prompting user to update their email address
When you send email to an email address that no longer exists, the receiving party (e.g. Gmail or Yahoo) will bounce the email back to you. If you listen to t