# File lib/net/pop.rb, line 611
    def mails
      return @mails.dup if @mails
      if n_mails() == 0
        # some popd raises error for LIST on the empty mailbox.

        @mails = []
        return []
      end

      @mails = command().list.map {|num, size|
        POPMail.new(num, size, self, command())
      }
      @mails.dup
    end