If a computer is not configured to open mailto links with an email client, there is nothing a website can do to open the client when such link is clicked. This is why contact emails on websites are often clearly shown so visitors can copy-paste them if mailto link is not working for them.
In Shapespark case, it could be better to use the HTML Label extension to show the email address as a mailto link:
Contact us at <a href="mailto:john@mail.com">john@mail.com</a>.
This way the email is visible and can be copy pasted if mailto is not working.