Firstly, it's default, just like mysql default come w/ user "root" and no password
Secondly, some people might use it w/ their isp mail server, some others might use phpmail class or other similar program, while some others might install mail server just like I did
Have fun,
[
test.jlbn.net] (Sample Test Codes for PHP, MySQL, SQLite, ASP.net, SQL, JSP)
[
www.jlbn.net] (Basic Guide for WAMP & Add-ons)