open default MUA with a hyper link

[Yann.K]

Hello.

I would like to do a hypertext link on a GUI, which launch a per default
mail user agent (with the "to" header documented).
To launch an url in a web browser i use webbrowser.open(url).
Do exist an equivalent command to run the per default MUA (like ie
webbrowser.mail_open(toto at example.com)?

Thank's for your help.

-- 
Yann.K