"If a user likes me enough to forward my newsletter to 60 of their friends and one of them -who also happens to be subscribed to the same newsletter- clicks unsubscribe because they don't take 10 seconds to read the subject -and then scroll through the email and still fail to recognize that this is a newsletter they had also subscribed to-, I'm out an extremely loyal reader/customer -who can't even recognize my newsletter- if I don't send that notification email."
and Two:
add to the end, "when both problems could have been solved at once by requiring the user to confirm the email address they wanted unsubscribed when they clicked on the link, thus providing both verification, and ensuring that a friend does not mistakenly do the same."
1. You receive a newsletter from [Retailer] and forward it to me.
2. I click unsubscribe
3. Ideally I'd enter my email. No damage done. But what if the unsub link is like a lot of unsub links, and it's something like: http://email.retailer.com/unsub.php?e=firebeyond@ycombinator...? Then you get unsubscribed, I've done nothing to make sure I don't get the emails anymore, and if [Retailer] doesn't send you a confirmation, you never get another email and you probably forget about them.
I like those "you have unsubscribed" emails for another reason beyond what you layed out.
I collect them so that I can keep a record of what I've unsubscribed from, so if I ever get spam from them again I don't have any doubt as to whether or not the sender broke their promise to unsubscribe me. It might just be me, but it is doubly aggravating to get spam and feel like I had previously unsubscribed but not be able to prove it. With proof I can be righteous in my anger and blacklist all future email from them. Without proof I am left to doubt my self and wonder if unsubscribing (again?) would be futile.
One:
"If a user likes me enough to forward my newsletter to 60 of their friends and one of them -who also happens to be subscribed to the same newsletter- clicks unsubscribe because they don't take 10 seconds to read the subject -and then scroll through the email and still fail to recognize that this is a newsletter they had also subscribed to-, I'm out an extremely loyal reader/customer -who can't even recognize my newsletter- if I don't send that notification email."
and Two:
add to the end, "when both problems could have been solved at once by requiring the user to confirm the email address they wanted unsubscribed when they clicked on the link, thus providing both verification, and ensuring that a friend does not mistakenly do the same."