Mit den Erweiterungen lightning und Sync Kolab kann man im Thunderbird auf ein in einem IMAP-Ordner abgelegtes Adressbuch zugreifen.

"Start with downloading and installing the Calendar and SyncKolab plugins, then create two folders, Contacts and Calendar, on your IMAP server. To configure SyncKolab's preferences, choose Tools -> Extensions and double-click on SyncKolab. In the Contacts tab, select the address book you want to synchronise, select your IMAP email account, and choose the Contacts folder. If you leave the Save to Imap folder check box unticked, SyncKolab will not upload changes in your calendar and address book, but download any changes from the IMAP account. Finally, use the Sync Contacts and Sync Calendar check boxes to select what data you want to synchronise. In the Calendar tab, select what calendar you want to sync and select the Calendar folder on your IMAP email account. Click OK to save the settings and close the window. Next, you have to add the SyncKolab button to Thunderbird's toolbar. Right-click somewhere on Thunderbird's toolbar and select Customize. Drag the SyncKolab button onto the toolbar and press Done. To start synchronisation, click on the SyncKolab button."