mailto: is only to send email. It will use the modest built in mail package to send but the package will close when the mail is sent. Modest opens faster for send than as total mail application. The following command line can be place in a shell file in /usr/bin and can be used to start mail quickly for sending a single email. I'm not the author but it came from a post in these forums.

dbus-send --print-reply --type=method_call --dest=com.nokia.modest /com/nokia/modest com.nokia.modest.MailTo string:mailto: