Two-factor authentication adds a second check when you sign in to webmail at mail.redmail.com. As well as your password, you enter a six-digit code from an authenticator app on your phone. The code changes every 30 seconds, so a password on its own isn't enough to get into your webmail.

You can use any standard authenticator app, such as Google Authenticator, Microsoft Authenticator, Aegis or 1Password.

What it protects: signing in to webmail, and mail apps that connect using Exchange, ActiveSync or MAPI (for example, your phone's mail app set up as an Exchange account). Once two-factor authentication is on, those apps need an app password instead of your normal password.

What it doesn't change: mail programs connected by IMAP, POP3 or SMTP, and calendar apps connected by CalDAV, carry on accepting your normal password. If you want those to stop using your main password too, give each one its own app password and keep your main password to yourself. See How do I create an app password?

Should you turn it on? If you read your mail in a web browser, especially on computers other than your own, yes. It takes about two minutes.