How can I tell what the default emailer is

I want 开发者_如何学Pythonto be able to submit an email from an application in response to a user action. Is there a way to detect if the user is using a default emailer. There always seems to be an emailer present (Windows Mail, or outlook express) but is there a way to check if it is actually in use or if the user may be using web based email

You could look at which application, if any, is registered to handle the mailto: URL moniker, which is at the registry key location: HKEY_CLASSES_ROOT\mailto\shell\open\command

It may be easier to just ask the shell to launch it for you, with a suitably constructed mailto: URI