Thunderbird 2.x handles signatures a bit different than Microsoft Outlook or Apple Mail. The signature is not part of the application as a setting, but is an external file, referenced in the account settings. The easiest way to create the signature is by plain text file, stored in your user account's home directory. Mozilla Thunderbird version 3.x features an integrated signature option in the Account Settings preference panes, though signatures can still be handled this way. How to create a signature in Thunderbird 3

Windows (XP, Vista, 7) with Thunderbird 2.x.x.x

  1. Open the 'My Documents' (Windows XP), or 'Documents' (Windows Vista, 7) folder and create a new text file called "signature.txt".
  2. New -> Text Document
  3. Enter your information into the file as you would like it to appear in the email's signature. Save and close the file.
  4. signature.txt
  5. Start Mozilla Thunderbird and go to the 'Tools' menu and choose the 'Account Settings' option, near the
    bottom of the list.
  6. Tools -> Account Settings
  7. Check the box next to 'Attach this signature:' and click the 'Choose' button to navigate to the location of the signature file, either in the 'My Documents' or 'Documents' folder.
  8. Account Settings
  9. Verify the new changes have been configured correctly by composing a new email message, the new signature will be at the bottom of the compose window.
  10. Compose