Amanda, Bacula, BackupPC Which has a reliable windows client?
Solution 1:
Bacula has a Windows client (that can be either desktop or server clients) that handles backups quite well. It utilizes VSS to create hot images of whatever you're looking to backup (works fine with Outlook AFAIK). You can set the desktop clients to use different ports than the default (9101 I think?) and port forward requests from their WAN router to each individual computer. Something with a VPN would be preferable, but not always possible.
Amanda and BackupPC use samba shares to backup - not exactly ideal, especially over WAN.
Additionally, Bacula has a bartpe plugin to do bare-metal recoveries, something that I haven't found for Amanda or BackupPC. The problem is that bare-metal recoveries are going to be tough (read: not impossible) to do remotely. I'm thinking your best bet with that is to have the clients boot to PXE where you recover the files to the client PC, or something similar. Either way, it'll be tough to set up.
Currently I use Bacula to backup 2 servers, 8 Windows clients, and 3 Linux clients, and it works very well. It has a number of front ends, with a python based graphical tool coming soon.
Recoveries are done to a server's local directory, then you can copy/push files to the clients that need them.
For what you're looking for, I think this fits the bill.
Solution 2:
Amanda has a Windows Client from zmanda which support VSS: http://wiki.zmanda.com/index.php/Zmanda_Windows_Client
Solution 3:
backuppc can also use VSS, via the rsyncd+vss method, check the url:
http://www.goodjobsucking.com/?p=62
It uses the windows RPC to remotely start scripts that setup the VSS and startup a rsync daemon.
i already build the needed "client" scripts and tools in here, so its easy to install:
http://caravela.motaleite.net/~higuita/backuppc/
i use this on +500 workstations and +50 servers with windows xp, windows 2003, vista, 7 and 2008 32bit and 64bits.
other package with the same scripts (version 1.1 doesn't seem to support 64bit, but do have wake-on-lan support):
http://www.michaelstowe.com/backuppc/
As it uses a windows service and no encryption, i recommend this for LAN usage, if you need security (as for WAN usage) you will want to setup a vpn to protect the traffic and the clients. check the openvpn, its easy to setup and secure.
If you need WAN and cant use a vpn, you can also check the cygwin ssh+rsync method:
http://sourceforge.net/apps/mediawiki/backuppc/index.php?title=CygwinSSHWindows
http://sourceforge.net/apps/mediawiki/backuppc/index.php?title=User_Scripts_-Client-_Windows_VSS