You have a couple of options. '''You can export address books directly from with Thunderbird''': * click on 'Address Book' * Select an address book. (Do not select 'All Address Books' as this is only a virtual address book). * 'Tools' > 'Export' * Choose where you want to save the address book. If a default address book - Suggest you modify the address book name eg If 'Personal Address Book' then change to 'PAB' as this makes it more convenient when importing at a later date. * Save as Type: ''''LDIF'''' is easily imported or ''''Comma Separated (System Charset) (.csv)' '''also easily imported, but also can be opened using eg: Excel and also easily imported into other email clients. * Click on 'Save' Repeat the above for each address book. Note: Whilst 'address book lists' can also be exported as a separate file, you should note that they cannot be imported back as a list, they can be imported as an address book. But please note all those contacts will already be in the associated address book. '''You can create a backup of the entire Thunderbird''' profile which would backup all profiles, mail accounts, emails (assuming you have downloaded full copies), address books (stored as .mab files), Calendar, message filters, preferences etc etc. Assuming you are using the default setup location: Exit Thunderbird and Copy the Thunderbird folder (as marked bold) to external drive for storage. '''Windows OS:''' * C:\Users\<Windows user name>\AppData\Roaming\'''Thunderbird'''\ The AppData folder is folder is a hidden folder; to show hidden folders, open a Windows Explorer window and choose "View > Options > Change Folder and Search Options. Folder Options window: View (tab) > under 'Advanced settings' > Hidden Files and Folders select: 'Show hidden files and folders". Click on 'Apply' and 'OK' '''Linux:''' Profile folders are located here: * ~/'''.thunderbird'''/ However, if you're using a third party build from Debian or Ubuntu, those builds store your profile folder here: * ~/'''.mozilla-thunderbird'''/ '''MAC:''' * ~/Library/'''Thunderbird'''/ The tilde character (~) refers to the current user's Home folder, so ~/Library is the /Macintosh HD/Users/<username>/Library folder.