As you get more tabs open in your browser, it can take a while to find the right one in the long list. To address this, I like to keep Outlook Email and Calendar tabs open and easily discoverable. The easiest way to do this is to pin the tabs, which will keep them at the top (vertical tabs) or left (horizontal tabs).
To pin the tab, just right-click on the Outlook tab in your browser. In the screenshot below I have vertical tabs enabled, which is not required (though I do recommend it).