Thunderbird saves annotations, bookmarks, favorite icons, input history, keywords, and browsing history (a list of pages visited). Data is saved at persistent "places.sqlite" and temporary "places.sqlite-shm" and "places.sqlite.wal".
Most users open the Thunderbird address book from within the email client, but it can also be launched separately. Mozilla Thunderbird by default comes with two address books, even though more can be added: 1. Personal book: For the most frequently used contacts. 2. Collected book: Collects addresses from email that you send.
Files for collected addresses: Since Thunderbird v78: "history.sqlite", "history.sqlite-wal". • Before Thunderbird v78: "history.mab".
Thunderbird stores cookie information in: "cookies.sqlite": Stores all cookies. • "cookies.sqlite-journal": The journal file for "cookies.sqlite". • "cookies.sqlite-shm", "cookies.sqlite-wal": Write-ahead log files for "cookies.sqlite". The file "cookies.sqlite" in the user's profile directory is used to store cookies between sessions.
Download history is saved in "downloads.sqlite" since Thunderbird 3 and in "downloads.rdf" before. It stores data to show downloads in Download Manager. Clearing download history can help to resolve slow downloads or program hangs.
"logins.json" stores encrypted passwords. It replaces "signons.sqlite", which had replaced "signons.txt". "logins-backup.json" is stored to recreate "logins.json".
Files for personal addresses: Since Thunderbird v78: "abook.sqlite", "abook.sqlite-wal". • Before Thunderbird v78: "abook.mab".
The default window layout is saved in the session file ("session.json"). It includes data on what tabs are open.