A simple utility using mailto: uri protocal. Will also detect if any mail client installed.
IsMailClientInstalledRoot() function will look for registry HKEY_CLASSES_ROOT\mailto\shell\open\command
for a command other than default C:\Windows\System32\run32.dll or simalar value.
If a custom value is found, a email client application might installed for all users.
IsMailClientInstalledForUser() function does simillar job, the only difference is that it looks for HKEY_LOCAL_MACHINE\SOFTWARE\Classes\mailto\shell\open\command\,
for any email client installed for current user.
mailto: command is used to compose a URI, then let windows system handle it.
In Windows 8 or later, default mail app is always an option. In Windows 7, if no email client is installed, Internet Explorer will handle this uri.
The address string is encoded by Uri.EscapeUriString(), and the title and body strings are encoded by Uri.EscapeDataString().
Note that we want whitespace in email title/body to be encode as %20, but not +.