The information located here should help: http://kb.mozillazine.org/Import_address_list_from_text_file If you only have email address. One per line. File saved as a text file. Tools > Import Select 'address book' and click on next Select : Text file and click on next import as "Tab Delimited (*.tab. *.txt)", un-checked all address fields except Primary Email, click on OK button. note: If you have eg; Joe Bloggs <[email protected]> then it should recognise the name fields as well, but you can map the fields to fit Thunderbird fields.