Phishing message detected

Hi,
We have enabled this plugin and enabled notification, but strangely due to this settings,
we are getting the phishing email notification from google having the subject line as below:

“Alert: Phishing message detected post-delivery for [email protected]”

Just for your note, we have set the From Address as [email protected] in the notification settings. So do you have any idea, why we are having such email notifications?