Anyone who can login to your email account can:
- impersonate you to others
- gain access to your online accounts
- spam your friends with fraudulent messages
- find out personal and financial information about you
In short, other people having access to your email is A Bad Thing™
Protect access to your accounts by using “Two Factor Authentication”. Your password is one “factor” by which you authenticate to a website. But passwords are guessed or stolen all the time. A second “factor”, like posession of your mobile phone, is a useful second check.
When you use two-factor authentication you raise a high barrier for anyone wanting to take over your account. Try it by giving your email password to a friend and asking them to login to your webmail from their computer. They won’t be able to, without having the unique, one-time code that your phone gives you!
You will need to enable two-factor authentication for each separate website (or service) that supports it.
While we’re here, it’s a great idea to enable two-factor authentication for: