I have had a little trouble with a recent installation of XAMPP v 1.7.3 which contains Mercury mail server v 4.7. The problem was that, although Mercury mail was showing as "Running" in the XAMPP Control Panel the test e-mail (page 38-39 of the Book) failed.

I am using Windows Vista, though this does not seem to be a factor.

I eventually discovered that the problem was due to module called MercuryX. Which I beleive is new to this version of Mercury. Others who have the same problem could try disabling MurcuryX as follows, which soved the problem for me:

In XAMPP Control Panel, click the Admin button next to Mercury (when Running).
Click Configuration, then Protocol Modules.
Uncheck MercuryX.
Restart Mercury in the Control Panel.

Hope this helps other.