List-Unsubscribe: <mailto:list@host.com?subject=unsubscribe>
as per RFC-2369 and use the same mailto link inside the mail body. This is convenient, conventional and solves the problem you describe, while also allowing users to add feedback as they see fit in the body.I don't see why you have to involve the web at all, but I can tell you that if I have to go through a bunch of bullshit when I want to unsubscribe I'll just mark it as spam instead. However appreciated and anticipated your newsletter is, you have to consider that most newsletter subscriptions are probably either accidental (failed to uncheck some box when signing up for something entirely different) or straight up unsolicited, and people like me will basically purge all their subscriptions without discrimination regularly as the crap builds up.