A very quick one. Been playing with the above class for generating emails in .NET 2.0, embedding images within HTML views which is rather cool. However, I noticed an unusual problem. The emails I generated in my test project would not send until I had exited the application. It was almost like it would only 'flush' the generated email once the application had unloaded. Interestingly, if I attempted to send the email using the 'SendAsync' method, it would fire the SendCompleted event but still nothing would come through until the application had ended.
The resolution? Turning off Symantec Anti-Virus's 'Internet Email Auto-Protect' facility from the 'Configure' menu. Once deselected, everything started behaving properly.
I cannot answer for any other AntiVirus packages - but its a good starting point if you're experiencing the above.
M