1. Determine the IP address or host name of the remote computer/virtual server.
2. Determine the TCP port number to connect with. (For example, you want to connect using SMTP port then TCP port is 25.)
3. Start menu => Run => cmd
4. Type the command. telnet hostname port_number
5. Hit enters.

Below mentioned are some Port numbers:
SMTP 25
POP 110
IMAP 143
HTTP 80
FTP 21