新安装 DP6 正式版 遇到 PHP mail() 函数问题，求解！

warning: mail() [function.mail]: Failed to connect to mailserver at "localhost" port 25, verify your "SMTP" and "smtp_port" setting in php.ini or use ini_set() in E:\xampp\htdocs\dp6\includes\mail.inc on line 191.
Unable to send e-mail. Please contact the site admin, if the problem persists.

这是提示，请问如何做才能让它正常呢？
我用的是XAMPP标准版。
如何才能在XAMPP上安装SMTP服务器？很是麻烦……