Telnet is a useful tool for troubleshooting issues related to SMTP and mail flow. This article describes how to test the process of an internal user sending mail to a remote user when basic authentication is required for relaying mail outside your organization.
You need to be a member of the local administrators group.
- Install Telnet. Telnet is a feature and is installed on a Windows using the Add Features Wizard in Server Manage or using the Turn Windows Features On or Off link in Control Panel
Use the procedure outlined in https://technet.microsoft.com/en-us/library/aa995718(v=exchg.65).aspx.