wcfm_vendor_registration_pending_email

add_action('wcfm_membership_registration', function ($member_id) {
    if (apply_filters('wcfm_is_pref_membership', true)) {
        $member_id       = absint( $member_id );
        $member_user     = new WP_User( absint( $member_id ) );
        $wcfm_membership_options = get_option('wcfm_membership_options', array());
        $membership_reject_rules = array();
        if (isset($wcfm_membership_options['membership_reject_rules'])) $membership_reject_rules = $wcfm_membership_options['membership_reject_rules'];
        $required_approval = isset($membership_reject_rules['required_approval']) ? $membership_reject_rules['required_approval'] : 'no';

        if ($required_approval == 'yes' && !wcfm_is_vendor($member_id)) {
            if (!defined('DOING_WCFM_EMAIL'))
                define('DOING_WCFM_EMAIL', true);

            $notification_subject = '[{site_name}] Your application is submitted';

            $notication_content = "Welcome {first_name},<br/>" .
            "You have successfully submitted your Vendor Account request.<br/>" .
            "Your Vendor application is still under review.<br/>" .
            "You will receive details about our decision in your email within next 48 hours!<br/>" .
            "Thank You!";

            $subject = str_replace( '{site_name}', get_bloginfo( 'name' ), $notification_subject );
            $subject = apply_filters( 'wcfm_email_subject_wrapper', $subject );
            $message = str_replace( '{first_name}',  $member_user->first_name, $notication_content );

            $message = apply_filters( 'wcfm_email_content_wrapper', $message, __( 'Pending for approval', 'wc-multivendor-membership' ) );

            wp_mail( $member_user->user_email, $subject, $message );

        }
    }
});