Telnet is a well known reliable protocol to communicate with different network hosts.It provides a bidirectional interactive communication facility between two hosts. If you want to use the Telnet application in Windows 7 then please note that it is not enabled by default. To enable it, you will have to go through the following steps.
First of all click Start, and choose the Control Panel option, now choose the program option from here.
Here locate and choose the Turn Windows features on or off option under the Programs and Features category.
The Windows Feature dialogue box will be launched, from here you can manage many of the features in Windows . You will see two options here, Telnet Client (connects to remote computer by using Telnet protocol) and Telnet Server (allows others to connect to your computer by using the Telnet protocol ), enable whichever option that you need. For contacting Exchange you only need the client.
Click the OK button and that’s it. Use this TechNet article to send an email using Telnet, always very useful when troubleshooting.