This happens often to me:
* Get email that I'd like to unsubscribe to
* Look for unsub info -- directed to "reply to this email" or, almost as bad, "enter your email address"
* Follow instructions
* Receive notice saying "Sorry, the email you entered [sent from] is not in our database"
Well thanks. We've gotten nowhere.
So the right way to design this should be a simple unsubscribe link w/ a unique token that executes the request upon clicking.
At worst, you can do what Constant Contact does and require the email address to be entered, but still provide a hint (i.e. "a....email@example.com"). This is still somewhat annoying, but I understand why they do it -- it likely reduces net unsubs since there's a second step involved. Pushing it, but thinking as a business owner as well, I get it.
Two benefits - 1) easier to remember my login per site and 2) if I start getting spammed as a result of my info being shared with third-parties, I can attribute the original offender to the e-mail address.
My mail server allows -- as an alternative to + so my users can work around braindead address regexes.
That + is frequently a cause of contention though, so I use a . (which was done via config when I ran my own mail server days gone by) and also have a catchall on google apps.
Also, the email address to which the message was sent appears clearly in the "To:" header.
Either you or your friend is misspelling their address (more common than you might think, I get opt-in mailing-list mail for firstname.lastname@example.org, intended for email@example.com), or you've encountered a bug.
The dots are for you to play around with, but the mail all goes to one account. Or, at least, that's how it works with my account.
Google's own firstname.lastname@example.org mailing list has this as the "To:" field:
And at the bottom of the message:
To unsubscribe from this group, send an empty message.
I had to ctrl-u and check the "Delivered-To:" and "X-Forwarded-For:" headers before I could unsubscribe.
(I'd tried to unsubscribe previously but the subscribed email account forwards to my main account so replying with an empty message didn't work. This thread prompted me to dig a little deeper and finally get one less piece of email per day - thanks HN!)
the majority use case here is that they're not malicious, merely spammy with good intentions.