KMail is the email component of Kontact, the integrated personal information manager from KDE.

Features

• Supports the standard mail protocols IMAP, POP3 and SMTP.
• Supports authentication via NTLM (Microsoft Windows) and GSSAPI (Kerberos)
• Supports plain text and secure logins, using SSL and TLS.
• Integration of international character sets and spell-checking (as-you-type and on demand)
• Native support for inline OpenPGP, PGP/MIME, and S/MIME.
• Reading and writing of HTML mail.
• Ability to display plain text only from an HTML mail.
• Allows you to receive and accept invitations.
• Integration with popular spam checkers, e.g. SpamAssassin, Bogofilter, etc.
• An optional spam probability meter can be displayed
• Powerful search and filter abilities
• Can import mail from many other clients
• Searching in IMAP folders fully supported
• Highly integrated with other Kontact components
• Encrypted password saving in KWallet
• Flagging and tagging of messages to aid sorting and recovery of information
• Supports mailing list management features
• Can replace text smilies with emoticons
• Displays the sender's picture or avatar if present in the address book
• Supports X-Face (b/w pictures in messages)
• Compression of attachments
• KMail supports Groupware functionality.