Summary: Thunderbird is a desktop mail client. It's a companion product to Mozilla Firefox. Besides standard email, it supports newsgroups, feed reading, and chat protocols (XMPP, IRC and Twitter), all with multiple identities or accounts. Through Mozilla Lighning or other plugins it's extensible into a full personal information manager. Out of the box it supports SMTP, POP3, IMAP, SSL/TLS, S/MIME, LDAP, RSS/Atom, and searching, filtering or grouping, labels, virtual folders, and comes with a spam filter.