If you are migrating from another email client, such as Outlook or Eudora, the first time you run Thunderbird you should get the Import Wizard (see Figure 10-1).
Figure 10-1. The Thunderbird Import Wizard.
Here is the current list of mail clients that you can migrate from. Remember that it is possible that support for other clients may be added in the future:
At the time of this writing, migrating from Eudora is not supported on the Mac.
Follow these instructions to migrate: