But what tag do you use to open a new email messege in gmail or other web based email "clients" / sites.
There is none. Which is why MAILTO: links are not user friendly. You should be using a scripted contact form on your sites.
Ask your host if they offer one as part of your hosting account. If not, and your server supports PHP, this Form-mailer script from DB Masters conceals your email address from prying eye email harvesters and it has spam controls built into its script -- including hidden field (honeypot), "sorta captcha," and time limits on submissions to keep robots from exploiting your forms. One script can run all the forms on your domain. Free to use if you credit the author; $20 if you don't.