When there are new items in my inbox, I receive a an email. That mail includes
email@example.com not only as the
From header of that mail (“sender”), but as the
To header (“recipient”) as well. So although that message was sent specifically to a single address, the header doesn't say so.
On the receiving side, this makes the message look like some kind of list message, which will get treated different from a personal message explicitely addressed to me.
Note that there is an unsubscribe link which contains the numeric ID of my user profile,
1580982 in my case. So the message is personalized. Also notice that according to comments below, including the recipient does work for bounty expiry warnings.
I wonder whether there is a good reason for the current behaviour. If not, I might turn this request for support into a feature-request instead, asking the real recipient address to be named in that mail.
Please ensure that messages specifically sent to a single person will include that person't email address in the
To header field of the message. Including the (user-)name as well would be an added bonus.