It happen yesterday (the 6 of october) at 3h50 am (UTC+1) and I wasn't able to access the server for nearly the whole day..
Actually nothing was lost and a backup is currently working. So I hope that tomorrow (or today if you prefer

If you send mails to the mailing during the down period, I think they may be lost forever... Actually I started by hand the mail server, so at least until the current backup is running, it will receive mail. Maybe with the long retry time some mailer use, they will not be lost.
I'll keep you informed.
Manoel