Hi Ian,
No thats not possible with that addon.
But you can use wordpress filter for that.
add_filter( 'is_email', 'uwp_restrict_email_custom', 10, 2 );
function uwp_restrict_email_custom( $valid, $email ) {
if ( strpos( $email, '@mycompany.com' ) !== true ) {
$valid = false;
}
return $valid;
}