Thunderbird is an email, newsgroup, news feed, and chat (XMPP, IRC, Twitter) client. The vanilla version is not a personal information manager, although the Mozilla Lightning extension adds PIM functionality. Additional features, if needed, are often available via other extensions.
- Message management: Thunderbird can manage multiple email, newsgroup, and news feed accounts and supports multiple identities within accounts. Features such as quick search, saved search folders (“virtual folders“), advanced message filtering, message grouping, and labels help manage and find messages. On Linux-based systems, system mail (movemail) accounts are supported.
- Junk filtering: Thunderbird incorporates a Bayesian spam filter, a whitelist based on the included address book, and can also understand classifications by server-based filters such as SpamAssassin.
- Extensions and themes: Extensions allow the addition of features through the installation of XPInstall modules (known as “XPI” or “zippy” installation) via the add-ons website that also features an update functionality to update the extensions. An example of a popular extension is Lightning, which adds calendar functionality to Thunderbird.