Yesterday, Stack Exchange sent me an email with the Developer Survey 2017 results. I am importing mail from various addresses, so it was only by chance I noticed it was sent to one of my older emails.
"Wait, this not the email I am using on SE".
I checked my profile, and yup, I changed my email address more than a month ago (In all communities, I have the same profile on all SE sites).
I know SE can send email to the new address as I received some other mail from the site about three weeks ago. So why is just this one email sent to an old address?