Export the WLM address book as a .csv file. It would make importing easier if you then opened the .csv file using eg: Excel, and modified the Column headers to match those used by Thunderbird. This link tells you the Column header names used in Thunderbird. * http://kb.mozillazine.org/Import_address_list_from_text_file eg: Thunderbird uses 'First Name' and 'Last Name', so if you currently have a column header called 'Name' which has both first and last name, then you need to modify the .csv file to separate the parts of the Name, so that instead you have 'First Name' and 'Last Name' column headers with appropriate content. Work through column headers to make sure they are the same title as those used in Thunderbird. Save the file. then import the .csv file to thunderbird. In Thunderbird Click on 'Address Book' 'Tools' > 'Import' select 'Address books' and click on Next select 'Text File (LDIF, .tab, .csv, .txt) and click on Next You then map the fields of the imported .csv to those of Thunderbird, which should now be quite easy as you modified the column headers.