Mailto links allow Gratavid to prepopulate an email directly in the default email client on your computer. Read below if you are having trouble with mailto links. Remember, its recommended to use Gratavid with Google Chrome.
To change the default app to Outlook, go to Windows Settings --> Apps --> Default Apps --> Email. Select Outlook as the default and voila - now, selecting mailto links in Chrome will launch Outlook.
If you want to make Gmail your default browser, follow Make Gmail your default email program.
If you have any issues, please create a Gratavid help ticket.