Mailtrack is no longer available in the Opera add-on store. Don't worry though, you can still use Mailtrack with your Opera browser. Here's how:
1) Open Opera and go to https://addons.opera.com/en/extensions/details/install-chrome-extensions/.
2) Install the Install Chrome Extensions extension.
3) Once you've done that, go to https://chrome.google.com/webstore/category/extensions and search for Mailtrack.
4) Click on the ‘Add to Opera’ button.
5) Click on the ‘Install’ button in the Opera Extensions Manager.
1) Open Opera and go to https://addons.opera.com/en/extensions/details/install-chrome-extensions/.
2) Install the Install Chrome Extensions extension.
3) Once you've done that, go to https://chrome.google.com/webstore/category/extensions and search for Mailtrack.
4) Click on the ‘Add to Opera’ button.
5) Click on the ‘Install’ button in the Opera Extensions Manager.