A short tale of building what matters and skipping the rest.
In cases like this, you can either anticipate all the likely possibilities and build lots of things to insure yourself against potentially bad situations, or you can ship what you’ve got, wing it, and be prepared to make changes as you go.
As is our style, we ran with the latter…and it was completely fine! Most people leave our original email quoted below when they reply. Then we click the Unsubscribe link for them. That’s it. It’s lo-fi and works in 99% of cases. If the quoted email isn’t there, Tom programmatically unsubscribes the person by hand. We have to do that a couple of times per week. No biggie at all.
So this is YAGNI in practice. You might be familiar with YAGNI as a programming-specific concept, but I think it’s just as applicable—if not more so!—on the design side.
Design is often a matter of diving headfirst into an unknown abyss, and preparing to modify your thinking based on what you learn. When you’re doing that, there’s no sense in trying to protect yourself from bumps along the way.