How far down the list do you get? These are all real issues with real newsletters or mailing lists I have at some time had the misfortune to subscribe to. Some of them are still filling up my spam box after multiple attempts at getting rid of them.

  1. Is it possible to unsubscribe? If not, why are you reading this? Shouldn't you be apologising to your users?
  2. Does every message explain how to unsubscribe? Or are you sending periodic reminders with newsletter metadata? *Shudder*
  3. Do I have to contact your domain to unsubscribe? Otherwise I'll assume the whole thing is a phishing attempt.
  4. Can I unsubscribe by email? Useful if bandwidth is low.
  5. Can I unsubscribe by replying to the newsletter? Much simpler than copying a newsletter+unsubscribe@example.org address or sending "unsubscribe newsletter" to mailman@example.org, especially on a phone.
  6. Can I unsubscribe by clicking a URL? The web is a powerful thing.
  7. Can I unsubscribe without typing anything? You're already generating unique emails, so it would be very easy to generate unique URLs.
  8. Can I unsubscribe in a single click? Why have two steps if you can have only one?
  9. Can I re-subscribe with a single click? For those silly accidents.