Emails from lets encrypt notifications
At this moment it is possible that emails are being received from lets encrypt about renewing certificates for domains that are not owned by you. This has been reported to Lets Encrypt and we will receive a solution soon.
We apologize for the inconvenience.
When these messages are considered unwanted you can make a (temporary) rule in the email to move this directly to SPAM. Or in another folder. Keep an eye on this announcement for when this is fixed.