Is this your gmail contact list? If so, - click to addressbook pane - click 'new addressbook' - click 'cardDAV address book' - enter gmail address on top line and then click 'continue' - Google will prompt for email address and password and will then authenticate the addressbook for use in thunderbird.

Unfortunately it is an outlook.com on my Thunderbird mail account on my Win 11 PC.

Your reference to Google caused me to infer gmail. For outlook, I believe you can select 'home', and the 'people' icon appears in left sidebar and, after clicking, the 'manage' option appears in upper right where you can export the addressbook.

Hi David What I am trying to do is export my Thunderbird address contacts book from the app on my Win 11 PC to my S20 phone. I still cannot understand. Cheers Alan

This is far afield from Thunderbird, at least for me. If I were starting from scratch, using Outlook, I would probably want the Outlook app on the phone. Since Outlook website can import addresses, my thought would be to create an export of the Thunderbird addressbook and import to the Outlook web account, presuming that the Outlook app would then use the addressbook.

Thanks for trying though. Very grateful

You're welcome, and I think that will work. Good luck.