The admin_email_confirm WordPress PHP action fires before the admin email confirm form is displayed.
Usage
add_action('admin_email_confirm', 'your_custom_function');
function your_custom_function($errors) {
  // your custom code here
}
Parameters
$errors(WP_Error): A WP_Error object containing any errors generated by using invalid credentials. Note that the error object may not contain any errors.
More information
See WordPress Developer Resources: admin_email_confirm
Examples
Display a custom error message
Display a custom error message if the email address is not valid.
function display_custom_error_message($errors) {
if ($errors->get_error_code()) {
echo '<div class="error"><p><strong>Error:</strong> Invalid email address.</p></div>';
}
}
add_action('admin_email_confirm', 'display_custom_error_message');
Log errors to a file
Log any errors to a file for later analysis.
function log_admin_email_confirm_errors($errors) {
  if ($errors->get_error_code()) {
    error_log('Admin Email Confirm Error: ' . print_r($errors, true));
  }
}
add_action('admin_email_confirm', 'log_admin_email_confirm_errors');
Display a custom message before the form
Display a custom message before the admin email confirm form.
function display_custom_message($errors) {
echo '<div class="notice"><p>Please confirm your email address below.</p></div>';
}
add_action('admin_email_confirm', 'display_custom_message');
Add custom CSS styles
Add custom CSS styles to the admin email confirm form.
function add_custom_css_styles($errors) {
echo '<style>
.error { background-color: #f2dede; }
.notice { background-color: #d9edf7; }
</style>';
}
add_action('admin_email_confirm', 'add_custom_css_styles');
Add custom JavaScript
Add custom JavaScript to the admin email confirm form.
function add_custom_js($errors) {
echo '<script>
document.addEventListener("DOMContentLoaded", function() {
alert("Please confirm your email address.");
});
</script>';
}
add_action('admin_email_confirm', 'add_custom_js');