If you have a Web Hosting, Reseller Hosting, or Managed VPS service with us, your emails are automatically being backed up. The frequency of backups varies, please refer to our 'What type of backups do you take and how often?' article for details.
With any of our other services, you need to make sure that you have backups enabled so that your emails are safe.
If you're looking to move your email data to us from another host, as long as you have cPanel this can be done with a Full cPanel backup file.
If you don't have cPanel, we recommend saving all of your email locally (usually done using an email client), and then once the email service switches over, you can move the local emails back onto the IMAP folder, which will synchronise them with the server.