The ZIP file attached contains a version 2.4 C# sample that is a working version of Authenticate. This code can be used as a starting point to create and test the other Messaging API functions. Authenticate should work simply by unzipping the project to a directory, build, and run.
The Authenticate function doesn’t have much use other than a quick way to test connection to the EasyLink System. When you perform a Authenticate function your user credentials are validated on our servers. All of the other Messaging API functions do a Authenticate as part of the function call.