The users are on a Windows Form where they fill out a fax cover sheet and hit Send. The remote fax service takes anywhere from two seconds to two minutes to return a result (long timeout).  By that time, the users have moved on to other things, having closed the form and opened another. What is the proper way to invoke the async method so that whatever form the users happen to have open, they will eventually see the success or the failure message?  
How to display a very delayed success message after async method call in WinForms after Form is closed
asynchronous programming;winforms