I am not sure what you mean by "address list". I don't see anything by that name in my Thunderbirds. So let's go with "address book". One way to share an address book is to synchronize it to an online address book. You can use Google Contacts and an add-on, gContactSync. It's not perfect, since there are mismatches between the two systems in how they store some data. Another method I have been using for a while is to sync using an add-on that lets you synch to various shared resources. https://www.ggbs.de/extensions/AddressbooksSynchronizer.html and I synch one particular address book to an IMAP server, so it is available to two different computers running Thunderbird. I have also used it to synch to a Dropbox folder, but I like the way that IMAP keeps it "internal" to Thunderbird. I don't have to take care to be sure that Dropbox has finished updating before starting Thunderbird. Note that it isn't real time; you download an address book, use it, and post it back some time later. You won't see changes other users are making, and they won't see your changes until you upload. And if two people each have a local copy, the last one to upload will overwrite the changes made by the other. It works fine for me, using one of two computers at two distinct locations, so I don't have clashes with multiple simultaneous users. Another possibility, but which I am not competent to help you with, is to use an LDAP server. I have the use of one of these at my workplace. It is effectively read-only, so you'd have to rely on a sysadmin type to maintain the server copy.