Your email messages are some of the most important files on your Mac, so they belong at the top of the list in your new backup regimen. Fortunately, you don’t need extra software to export, back up, and import your mail. Everything you need to do the job is in Mail, Outlook, or Thunderbird—and this guide. Just connect an external drive to your Mac and get started.
If you use Thunderbird, you’re probably used to getting by without the bells and whistles –– or price tags –– of other, flashier mail clients. Who needs ‘em anyway, even for important operations like migrating to a new Mac or Thunderbird installation? Even if you don’t use Time Machine to back up your Mac’s drive, it’s easy to back up and restore your Thunderbird messages.