As described in the Profiles - Where Thunderbird stores your messages and other user data article, Thunderbird saves personal information such as messages, passwords and user preferences in a set of files called a "profile", which is stored in a separate location from the Thunderbird program files.

When you install Thunderbird it creates a profile called "default". This profile is used automatically. However, you can create additional profiles, each with their own set of account configurations, messages, etc. (Note, however, that you can access multiple email accounts within a single profile as well.)

To create additional profiles, use the Thunderbird Profile Manager.

Enabling the Profile Manager

The Profile Manager is used to create and delete profiles, and to select the profile to use for a Thunderbird session. It is not displayed by default. Instead, you must invoke Thunderbird with a "switch" that makes the Profile Manager appear. After that, the Profile Manager will be displayed every time Thunderbird starts, until you check the Don't ask at startup option.Use the selected profile without asking at startup option.

To enable the Profile Manager:

Creating and deleting profiles

When you load Thunderbird, a dialog is displayed that allows you to choose a profile.

To create a new profile, click the Create Profile... button. After specifying a name for the profile, you may also specify a custom location for the profile folder (or click FinishDone to use the default location).

To delete a profile, highlight the profile in the Choose User Profile window and select Delete Profile.... Note that you cannot delete a profile by simply deleting the profile folder from the disk. It will still be displayed in the list of available profiles.

See the Profiles - Where Thunderbird stores your messages and other user data article for information about locating the profile data files on a file system and making backups.