And who pays for the bandwidth and diskspace. I will be wanting a minimum of 20Gb. A usb key sound like a much better and much faster solution. Like many people your looking at backup as a series of small unrelated bits of information. Personally I would be far more concerned if my mail all disappeared. Filters a lot less so. But fortunately I have a copy of windows with a back program (funny how Microsoft missed that for home versions) so I can schedule backup of all my data on a regular basis. For those without such a program, Thunderbirds profile can be backed up in a number of ways. I discuss some of them here http://thunderbirdtweaks.blogspot.com.au/2012/02/backups.html Or you just backup the msgfilterrules.dat files in the profile. One for each account with filters. Interestingly one of the tasks the Firefox people have on a daily basis is explaining that sync is not a backup and that people who have lost their bookmarks etc can not get them back from that "backup"