I just managed to add Active Directory authentication on the NAS-XSR SMB using an SBS 2003 R2 server. The documentation is a bit lacking in instructions, but it's not too hard to determine what needs te be set. Let me know if I can help you clarify this bit in the documentation.

But here's my problem: Once you set this authentication, you'll be swamped by emails each time you reboot your AD server. It seems the NAS checks the AD once a minute or so to determine authentication stuff. If the AD is not running, you'll get an email or two. This quickly clogs up your mailbox with messages which are all basically the same.

Perhaps you can change this functionality to send an email every x minutes, where x is user definable.

Merry Christmas!