I got a case that is the body content mail is Japanese so when i put it in mailto , maybe they encode that content . So the url mailto:... over 2000 characters. So mail cannot open it.
So i thinking do we have some ways to open an mail then insert content later or another way to archive this problem ? Thanks
No.
That would require the browser and the email client to provide an API that would allow the email content to be manipulated.
They don't.