EWS, MSG.exe and Windows Services

Task is to send notification to a user whenever an email arrives into a public folder. I created a windows service with EWS subscription service and whenever NewMail or Created event occurs, the OnEvent creates a MSG command to send a notification to the user that email is waiting for him in the public folder.

For sending the notification I am using the Process class:

string sCMD = @"MSG.exe " + user + " /Server " + pc + " /Time 0 " + msg

System.Diagnostics.ProcessStartInfo startInfo = new System.Diagnostics.ProcessStartInfo();
                startInfo.FileName = "cmd.exe";
                startInfo.Arguments = "/c " + sCMD;
                startInfo.UseShellExecute = false;
                startInfo.CreateNoWindow = true;
                startInfo.RedirectStandardError = true;

                startInfo.WindowStyle = System.Diagnostics.ProcessWindowStyle.Hidden;
                System.Diagnostics.Process proc = new System.Diagnostics.Process();
                proc.StartInfo = startInfo;
              
                proc.Start();
                string error = proc.StandardError.ReadToEnd();
                proc.WaitForExit();

I am receiving the following error message:

‘MSG' is not recognized as an internal or external command, operable program or batch file.

When I ran the same function from a forms application, it works. When I copied it to the Windows Services application, it is throwing the above error.  Any light on how to fix this  will be of great help.

Appreciate your help.