Thunderbird has two default address books. They are called 'Personal Address Book' and 'Collected Addresses'. These two address books can be copy pasted directly from one profile to another overwriting the current one.

All *.mab address books can be imported using an addon tool: MoreFunctionsForAddressBooks

• https://freeshell.de/~kaosmos/morecols-en.html

The Thunderbird Profile folder is a hidden folder. To Make hidden files and folders visible

• http://kb.mozillazine.org/Show_hidden_files_and_folders

To Access the Profile folder name in your current Thunderbird: 'Help' > 'Troubleshooting Information' click on 'Show folder' button. a new window opens showing the contents of your profile folder name.

Close Thunderbird now - this is important It must be closed before doing anything in the profile folders.

OR access directly: Info on where it is stored will depend on OS.

• http://kb.mozillazine.org/Profile_folder_-_Thunderbird

'Personal Address Book' will be called 'abook.mab' 'Collected Addresses' will be called 'history.mab'

All other address books created by you will have a .mab extension. they may have a name specified or use abook with a numeric suffix. eg: abook-1.mab

If you use the MoreFunctionsForAddressBooks addon tool. Download .xpi file to desktop or downloads folder.

in Thunderbird Tools > Addons OR Menu icon Addons click on gear wheel icon and select 'Install addon from file' locate the .xpi file and click on Open Restart Thunderbird.

click on 'Address Book' You will need to actually select an address book as the following option is not available under 'All Address books'. Tools > MoreFunctionsForAddressBooks > Actions for address books > Import address book from .mab file It will ask you create a new address book name. click on OK then locate the .mab file.