A few weeks ago someone asked on the MSDN forums how he could use the mailto: protocol to send a multi-line email. The trick is to use %0D%0A in lieu of \r\n.
Here’s a small C# code snippet that shows how to do this :
string command = "mailto:abc@abc.com?subject=The Subject&body=Ln 1%0D%0ALn 2"; Process.Start(command);