# File lib/rmail/header.rb, line 850
    def address_list_assign(field_name, addresses)
      if addresses.kind_of?(Array)
        value = addresses.collect { |e|
          if e.kind_of?(RMail::Address)
            e.format
          else
            RMail::Address.parse(e.to_str).collect { |a|
              a.format
            }
          end
        }.flatten.join(", ")
        set(field_name, value)
      elsif addresses.kind_of?(RMail::Address)
        set(field_name, addresses.format)
      else
        address_list_assign(field_name,
                            RMail::Address.parse(addresses.to_str))
      end
    end