Hacker News Reader

Comment by ilyt | Hacker News Reader

Recipient A gets their personalized copy, as does recipient B

Recipient A then clicks reply-all, now everyone has copy that was personalized to A. They might even notice subtle differences between them.

View on HN

But how did recipient A get a personalised copy if the mail with that copy was sent to a list of recipients?

Edit: WP has the Tesla story with the counsel forwarding his copy to everyone in a new mail (presumably trying to be helpful?) So not a case of reply-all disease

https://en.m.wikipedia.org/wiki/Canary_trap

Email round one: individually-watermarked copies are delivered to individually-addressed individuals. More elaborate systems might watermark such emails en-route, though that's ... less likely. A and B each wind up with individually-identifying copies of the email.

Email round two: A REPLIES ALL to their individually-watermarked copy of the email, delivering it to ALL employees (or some nontrivially large sample), by which B AND EVERY OTHER RECIPIENT now contains A's watermarked copy.

Email round three: B OR ANY OTHER RECIPIENT OF A's REPLY ALL can now leak A's watermarked copy of the email. Watermarking NO LONGER identifies the leaker.

> But how did recipient A get a personalised copy if the mail with that copy was sent to a list of recipients?

Watermarking added by the mailing-list manager software?

But in this case recipient B must have already had that one, as they were in the reply all for recipient A. If you sent me a personalized email and send it only to me, then my reply all isn't going to give my personalized version to anyone else but you- and presumably you trust yourself not to be the leak.

Reply-All would not include any other recipient in a standard, personalised mail out - unless the "To" or "Cc" fields were manipulated to give the impression that personalised email A went to everyone equally, but I think that would probably require some custom mailserver tweaks?

Reply on news.ycombinator.com