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