The job has enabled "Send separate e-mails to individuals who broke the build". When the job fails, the notification is sent to all the previous emails held by the committer instead of sending it only to the email set in Git commit that failed during the build.
This is causing unwanted noise.

I also couldn't find any documentation on how git-plugin / Email Notication fetches the email of the git committer for a git commit that failed during the build.

Jenkins Ver 1.580.2
Git Plugin Ver 2.3.4