I got a reply from a user today with the following email below. I have never ran into this before. What causes this and how can it be stopped?
Hi username,
This notice confirms that your email was changed on website name.
If you did not change your email, please contact the Site Administrator at
admin@sitename.com
This email has been sent to username@gmail.com
Regards,
This is a feature since 4.3.0, as part of WordPress’s improved security measures (check out the source on the WordPress code reference).
You can disable it with the following filter:
add_filter( 'send_email_change_email', '__return_false' );
