content: -- based on 
  -- http://support.indev.ca/kb/mao-advanced-techniques/applescript-to-archive-old-messages-in-current-mailbox
  set DestinFolderName to "Archive" -- mailbox to move messages to. If the account of a specific message does not have such a mailbox, no action will occur.
  
  set ArchiveDate to (current date) - (30 * days)
  
  tell application "Mail"
      set msgs to every message of message viewer 1 whose date received is less than ArchiveDate
      repeat with aMsg in msgs
          set acct to account of mailbox of aMsg
          
          -- see if the account of the message has an archive mailbox
          if name of every mailbox of acct contains DestinFolderName then
              -- if so, archive the message
              set archiveFolder to mailbox DestinFolderName of acct
              move aMsg to archiveFolder
          end if
      end repeat
  end tell