The first, Xsan 2.2.1, improves file system reliability and cvfsck repair utility. This update is available for Mac OS X 10.6 Snow Leopard and Mac OS X 10.5 Leopard. There's also an updated version of the Xsan uninstaller.
Next, Mail Services Update 1.0 addresses issues affecting overall mail service reliability and performance. This update is available and recommend for all users on Mac OS X 10.6 Snow Leopard.
These updates are available in Software Update, or from Apple's Support Downloads page.