For a long time, Thunderbird has had read-only access to the mac address book. ISTR reading that this has changed recently, but as a non-mac user, I can't check for myself. "Read only" means that Thunderbird can't modify the mac address book.

However, you should be able to store Mailing Lists in the Personal Address Book. If in general you can't make any changes to an address book, that might indicate the underlying data file is corrupted. The usual way to repair it is to export its contents to an LDIF file, delete the original broken address book, then re-create it by importing from the LDIF file.

Since the Personal Address Book and Collected Addresses are "special" and hard-coded, you won't be allowed to delete them. To remove either of these, you need to locate your profile folder, close Thunderbird and delete abook.mab for Personal Address Book, and history.mab for Collected Addresses.

other than not knowing what an LDIF file is, i think my problem is solved. b/t your comment about "thunderbird having read only access to the mac address book", and a conversation moments ago with my computer friend explaining to me that thunderbird actually USES the mac address book - that is, the data is not actually stored in thunderbird so everything remains in the old mail address book app. so, if i want to change or delete one of the groups i imported from there, i have to go "back there" and change it. makes so much sense when you understand. ha. thank you, zenos, this was extremely helpful.

If you're not happy with jumping between address books, you could look at Tools|Import in Thunderbird's Address Book and see if it invites you to import the mac address book into Thunderbird. At the moment Thunderbird can show you the mac address book, but it's not quite accurate to refer to this as having been "imported".

This still leaves me uneasy about what's going on in your Personal Address Book, as you ought to be able to add and edit entries, including Mailing Lists.

yes, i understand i am accessing the mac address book. that was my big ah ha. i used the thunderbird "import" feature to begin with to add my mac addresses, they are just not technically "imported" as you say. when i click on "address book" in the thunderbird window, my computer is literally going back into my mac address book to retrieve the address, even tho it appears as if it is stored in thunderbird. nowhere, in any troubleshooting i have run across, is there this simple explanation and i'm not sure i would have ever figured out what was going on.

i went back into my mac address book, made changes and deletions to the groups i wanted to change/delete, and they showed up as changed in thunderbird. i CAN change things around in my personal address book, that was another issue that has been resolved with this one. thank you again for your expertise, zenos.