My best recollection is the current import process does not support bringing in outlook groups.

For your present situation, are you saying you created created an Mailing List (contacts group) and populated it with contacts, and now a few weeks later the list is empty?

Thank you Wayne,

Yes, I created the group addresses using Thunderbird tools and I tested at least one of the groups a few weeks ago. This week I needed to add other contacts to a group that was created a few weeks ago (may not have been tested). That group reports "no contacts available," as do all (9) of the groups I created a few weeks ago. I choose to switch to Thunderbird because everytime I buy a new computer I need extensive expert help to make Outlook work again. I have used Outlook for at least 30 years and in May 2025, when I replaced my computer, I spent at least 8 hours assisting Microsoft experts fixing my Outlook. I'm guessing that previous experts fouled things so that current experts had trouble reparing the previous mess. Shame on Microsoft for making the transitions so difficult. Now, I'm trying to like Thunderbird - it has excelent reviews. Of course, I don't know how to do much using Thunderbird. And I don't expect to be fluent for some time. Could I have done something stupid to clear everyone of my group addresses? Can Thunderbird repair the damage?

Thanks, Stephen Thompson