KMail

KMail is the e-mail client of the KDE desktop environment.

It supports folders, filtering, viewing HTML mail, and international character sets. It can handle IMAP, dIMAP , POP3, and local mailboxes for incoming mail. It can send mail via SMTP or sendmail.

Spam and filtering

KMail uses two special filters to provide a modular access to spam-filtering programs:

Send this e-mail to a program allows any program to be specified, and when that KMail filter is activated, the program will be run and supplied with the contents of the e-mail as its standard input.
Pipe this e-mail through a program not only sends the e-mail to a specified program, but replaces the e-mail with the output of that program. This allows the use of systems such as SpamAssassin which can add their own headers to a piece of e-mail.

These modular filters can be combined with text filters to detect (for example) e-mail which has been flagged by SpamAssassin by looking for the special headers it added.

KMail allows manual filtering of spam directly on the mail server, a very interesting feature for dial-up users. Emails that exceed some threshold size (standard is 50 kb, but it may be set any value) are not automatically copied to the local computer. With "get, decide later, delete" options, KMail lists them but does not download the whole message, which allows the deletion of spam and over-sized messages without wasting time.

Cryptographic support

KMail supports the OpenPGP standard and can automatically encrypt, decrypt, sign, and verify signatures of email messages and its attachments via either the inline or OpenPGP/MIME method of signing/encryption. KMail depends on GnuPG for this functionality. As a visual aid, KMail will colour verified email messages green for trusted signatures; yellow for untrusted signatures; red for invalid signatures; and blue for encrypted messages.

KMail also supports S/MIME messages as well as Chiasmus , a proprietary cryptographic system created by the German Federal Office for Information Security (BSI).

Groupware support

When used as part of the Kontact personal information manager suite, KMail can act as a groupware client, sharing contact lists, e-mail, calendars, and notes between users.