I was told to post my comment here from Jenessa Peterson. What has happened is that we receive notifications for a site that we no longer are hosting, and do not have access to. Could you please remove us from mailing list from these 2 specific sites? The mail is coming to our inbox: info@eclass4learning.com I am not sure what "mail content" is needed. Thanks!
Yes, this is correct: it is per email address. Newer renewal notification emails have a note about this right next to the unsubscribe link. It looks like the one above is an older email from last year.
Yes. You are unsubscribed from all emails for the next year. There are instructions on the url you didn't read for a workaround (Expiration Emails - Let's Encrypt), you basically have to update the email address attached to your account.
The action you wanted to take in this situation was to do nothing. You'll only get one (maybe two?) expiry notifications per expiring certificate, and nothing post-issuance.