In order to keep former employees in your orbits, leading firms have an alumni programs that:
Whether you have a formal alumni program or you use less formal links, staying in touch with former employees may lead to new business, create market intelligence, and occasional rehiring of good people. Doing this will also increase the company’s attractiveness for career-minded people who know that working for your company will allow them to access a larger network of people.
Surely, the way you and your company depart with employees will determine the future relationship. For a better relationship, you should congratulate the person and wish luck for her/his career, ask the HR department to wrap up the termination issues, demonstrate appreciation for the contributions, continue to communicate with the departing person and inform the person on employment opportunities of the company.