Mailto link in chrome opens new tab
This happens in because you have not set your default mail in that browser and so the browser is treating your link like a page Copy and paste into a new browser window for directions on how to set the default mail.
Below are the URLs for 4 most common web browsers
Internet Explorer https://support.microsoft.com/en-us/help/555566
Firefox https://support.mozilla.org/en-US/kb/change-program-used-open-email-links
Google Chrome https://support.google.com/chrome/forum/AAAAP1KN0B0oxPLcXhbt9w?hl=en