The best professional suffix to use depends on occupation and level of certification. For instance, a professional suffix cannot be used for a qualifying degree. A suffix should not be used as well as a prefix where both indicate status, such as Dr. as prefix and MD as suffix.
Where no dedicated professional suffix is appropriate, Esquire is used. For example, lawyers in North America commonly use Esquire as a professional suffix, which can be shorted to Esq. In professional communications, Esquire is used in place of the prefix, Mr, but is not often used in casual communications outside of the legal profession.