1. Telnet to port 25 of your target SMTP server.

Open command prompt windows and type

C:\telnet mail.YourDomain.com 25

Connecting To mail.YourDomain.com..._

Mail server will respond with successful message

Connected to mail.yourdomain.com .
Escape character is '^]'.
220-svx.premiumwebserver.com ESMTP Exim 4.69 #1 Sun, 27 Sep 2008 08:25:39 -0500
220-We do not authorize the use of this system to transport unsolicited,
220 and/or bulk e-mail.

2. To check POP3 connection, Open command prompt windows and telnet port 110

C:\telnet mail.yourdomain.com 110

Connecting To mail.yourdomain.com...

The server should respond with a generic welcome message.

Connected to mail.yourdomain.com
Escape character is '^]'.
+OK Hello there.

Note: Telnet is not installed on Windows Vista by default. To solve this problem, go to Control Panel, then Programs, then under Program and Features select Turn Windows Features On/Off, then scroll down and click to select the Telnet Client.