If your system requires subscribers whose email address changes to unsubscribe the old address by hand and then sign up again with the new address (maybe even being asked nasty questions again), chances are even the most avid reader will wonder whether your newsletter is worth the trouble.
Make it Easy for Subscribers to Change Their Email Address
That's why you should
- provide subscribers with an easy to way to change their address.
The most simple approach is probably also the best:
- on the page that allows readers to unsubscribe, offer another field where they can subscribe a new address (carrying over all their data) and
- change the link to that page in the newsletter from "unsubscribe" to "unsubscribe/change address".