Need to set mail to open google mail: (also see
stackexchange)

This only means email will open by default in another email client.
If you want mailto: links to open in Gmail on Safari or Chrome or any
other browser, however, then doing this won’t work. You actually have to
cut out Mail altogether and make the changes to the browser itself.
On Chrome, it’s incredibly easy to default open mailto: links in
Gmail. You can simply open a Gmail window and click on the gray double
diamonds next to the bookmark star. Out pops a dialog asking if you want
to allow, deny, or ignore. If you choose “allow” or “deny” then either
way, you’re set.

If you later change your mind, such as if you realize you do want to
open mailto: links in Gmail, then you can change it. Type
“chrome://settings/handlers” in the location bar and choose (or remove)
gmail as your mail handler.

If you use Firefox, it’s also easy. Open the preferences (“Command +
,”) and click the “Applications” tab. Scroll through the “Content Type”
until you find “mailto” and then choose your default “Action” from the
right column.
Details