Sort has two arguments before the *search_criterion* argument(s); a parenthesized list of *sort_criteria*, and the searching *charset*.Note that unlike ``search``, the searching *charset* argument is mandatory.There is also a ``uid sort`` command which corresponds to ``sort`` the way that ``uid search`` corresponds to ``search``.The ``sort`` command first searches the mailbox for messages that match the given searching criteria using the charset argument for the interpretation of strings in the searching criteria.It then returns the numbers of matching messages.