def mails(element_key, options = {})
      parameter = { query: options }
      parameter[:basic_auth] = @auth

      response = self.class.get("/elements/#{element_key}/mails", parameter)
      return response['ElementList'] if response.success?
    end
def mails(element_key, options = {})
      parameter = { query: options }
      parameter[:basic_auth] = @auth

      response = self.class.get("/elements/#{element_key}/mails", parameter)
      return response['ElementList'] if response.success?
    end
Loads the list of mails on folders,
 +options+ can have these values: size, page, attribute = ALL|NONE|GLOBALLISTER|SECONDARY|EXPLORER
 Returns a list of elements
 It returns nil if no element with this elementKey was found