# File src/rails-1.1.6/actionmailer/lib/action_mailer/vendor/tmail/facade.rb, line 81
    def addrs2specs( addrs )
      return nil unless addrs
      list = addrs.map {|addr|
          if addr.address_group?
          then addr.map {|a| a.spec }
          else addr.spec
          end
      }.flatten
      return nil if list.empty?
      list
    end