And what about Backup Mail Services (or Backup MX) ?
mail backup service acts as your second priority mail server. If your mail server cannot be reached, the mail will be routed to dnsExit's mail backup server and wait in queues. Our server will continually check to see if your mail server is back online. Once your mail server is detected available, the queued mails will be forwarded to your mail server
sound great!
Maybe there is not such a service for free, somebody here know about one accessible and serious ?
here I found a guys in a fast googling... looks cheap and ok:
http://www.dnsmadeeasy.com/s0306/prod/mailbk.htmlLet me know if you have some ingo regarding this service.