1) Use a different communication channel for sending the ID+password than just e-mail. For example, we already have a channel for automatic updates, online backup and reporting. We could use this channel to send the connection data to our servers, where any available tech could pick them up, click a link, which would execute the Viewer with the right command line directly, without having to type anything.
2) We could connect to our application's database, checking for any relevant information before even making the connection. We could, for example, read the customer's name from the database (to be displayed to the tech handling the case), or check for their support level in our systems (e.g., do they even have a support agreement? Do they have a specific tech assigned to handle their cases?).
I imagine a simple DLL with one exported function, such as: