Select the address book right click on the highlighted address book and select 'Export' OR click on the 3 dot icon that appears when you select the address book and select 'Export' Choose where to save it eg: flashdrive SAve as type: select 'Comma Separated (UTF-8)(*.csv)' Useful for importing again or importing to another device or software. You can also open a 'comma separated' file using eg: Excel or Open Office Calc etc Save as Type: select 'LDIF (*.ldi, *.ldif)' if you only want to import back into Thunderbird or another Thunderbird on another device.