If you had a pop mail account and you accessed the Account Settings, selected the pop account, clicked on 'Account Actions and selected 'Remove account' Then the pop account will be removed from the folder Pane but it should still be lurking in the profile name folder. Create an existing mail account for the same email address and set up as pop using appropriate server settings. Then point that new pop account to use the old pop account settings. See info here: http://kb.mozillazine.org/Thunderbird_:_FAQs_:_Recover_Deleted_Account Image below shows where you locate 'Local directory:' so you can select the old pop mail account.