Depending on your particular email set-up, all emails can be accessed online. You will need your email address and password.
To access your email online simply enter into your web browser https://yourdomain.com/webmail Then enter your email and password. You can then select a webmail client.
If you have an email client, such as Outlook or Thunderbird set up to remove email from the server, the above method will not allow you to view your email, as your email client downloading your email to your local computer. However, in the event that your email client or computer where your email client is installed becomes inoperable, you may be able to access your webmail with the method above, until your local client has been restored.