In formal business dealings, correspondence, business meetings it was always best to refer to people by their title whether it be plain Mr or Your Excellency, etc unless invited to do so by the respective parties, and this normally in private meetings. Titles always used in the presence of third parties whether they be your own or the other parties employees and that was respect and etiquette. After hours you can be Fred, Jim, John, Julio etc depending upon the development of the business and personal relationship. Never saw the need for Christian (or first name) names shipboard, the Chief liked being called Chief, the Bosun liked being called Bosun and this went on in cabins and even the ship's bar (if they had one). Just my experience and views.