Before enabling 2-factor email authentication for your WordPress site, you'll need to verify you can receive emails. This verifies your site can send emails and that your account can receive emails sent from your site.
So, when you go to the Login Guard module => 2FA-Email => and click to Enable Email Authentication option, verification email will be sent.
Please note that this email will be sent to the email address of the site, outlined in the admin notification. (screenshot below)
To confirm that your site can send emails, simply go to your inbox and click the verification link in the email you received.
The email subject will be "[your-site-name] Email Sending Verification".
Important: If you get a warning that the link has already expired, please ensure that, when you're clicking the link, it is opening up in the same browser where you're logged into that WordPress site and turned on the feature.
If for some reason you need to resent this verification email or you want to disable 2FA by email, you may do so directly from this admin notification.
To resend verification email, just click "Resend verification email" link. To disable 2FA by email, click ""Disable 2FA by email" link.
Important: To enforce users for email authentication, you'll need to select the user roles first. Please see here.
For more information about email-based 2FA settings, read the article here.