We have made an enhancement to note-related email notifications to include opportunity references in the subject and body of the emails.
When an opportunity is referenced in a note and you choose to send an email notification for the note, the ID number of the referenced opportunity now appears in the subject of the email, and a link to the opportunity record appears in the email body. If you reference multiple opportunities in the note, the email subject denotes that there are multiple references, and the email body contains links to all of the referenced records.