heh... But links to unsubscribe makes no sense when you're not sending a regular newsletter. You're just emailing them once. Plus it removes the sense of any personalization.. "Click here to unsubscribe? But I thought you were sending me a personal email!"
There is no subscription. What are you unsubscribing from? Or just consider all such emails to be unsubscribed automatically after this one email, making a link pointless.
The reason for this is really for mass emails. It really should not apply when you send a few hand-written emails to a few people.