How to telnet under Vista?

Please follow the steps below:

By default there's no "telnet" function installed in Vista. So you have to enable it.
Go to control panel -> Choose Program and Features -> Turn Windows features on or off -> Then find a row called "Telnet Client" and tick it
Click on Start -> Run. Type command into the dialog box, then click OK.
You should be able to find a black Dos command prompt. input the command that we ask you to test in the format of "telnet hostname port". For example, telnet mail.yourdomain.com 25
The telnet result appears