If you cannot access mail via browser then this instruction page will provide assistance. Generally, User access personal mails on Brower. Irrespective of browser, mail issue can be faced in any internet browser. Safari and Google chrome are the most common browsers used by any typical Mac user. Here are some easy steps that will help you How to troubleshoot Mail issue in browser
Step 1: Make sure that internet connection is working fine. Also, ensure that you are entering correct username and password. To make sure that webmail server is working properly, check the mail on any other browser or device.
Step 2: Sometimes browser blocks the webmail website. Do check it and ensure browser is not blocking webmail. If still you are facing issue then Reset the browser.
Step 3: Delete cookies and caches from the browser. Navigate to /library/preferences. Find the Plist for browser and delete it. Now try to access the mail. If still not working, reinstall the browser.