[jonemo]

After reading the linked article and thinking WTF-hows-that-supposed-to-work, then reading the linked article, and reading the linked article again, I think I found the big caveat: It relies on unstandardized undocumented behavior of some email clients. Specifically, it doesn't work in Gmail.

But the problem actually seems real, makes me glad that I am not an email marketer. If you provide a one-click unsubscribe to your users, you don't want them to give somebody else that link. Reading through this HN thread, I see two and a half other solutions mentioned:

(1a) Require users to enter their email address on unsubscribe. I hate that one because frequently it's really hard to figure out at which of my email addresses the message first arrived.

(1b) Require users to confirm the unsubscribe The better version of the unsubscribe forms from alternative (1) have the email address pre-filled, which wouldn't stop someone who knows what they are doing from unsubscribing others. But it gives those unsubscribing others unintentionally a hint about how they ended up with that message.

(2) Send an email confirmation after unsubscribe This way you can just re-subscribe if one of your friends unsubscribed you. Looks like some people in the discussion below like this approach, others hate it.

If I had to pick, I'd probably chose (2) because that's the only way of making sure an accidentally unsubscribed user notices what happened.

[kevinconroy]

As a developer who has to do some email marketing, I can say "It doesn't work in Gmail" is a shame, but not a non-starter.

If you're used to HTML5 and CSS3, HTML for email will make your eyes bleed. Many CSS2 (!) attributes have quirks, few are cross-email client compatible. It's recommended that you inline your CSS, rather than using a <style> block, to ensure that it works as widely as possible. Even the <p> tag is considered a no-no as not every client renders it properly.

So while this doesn't work in Gmail, the <p> tag doesn't work in Yahoo!. #fml