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

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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