The user-friendly, lightweight, and fast email client Latest Release: 3.21.0 / 4.3.0 (News), on 10 June 2024

Features

Claws Mail includes all of the features you'd expect, including, but not limited to:
Multiple accounts
Threaded display
Filtering
Mime attachments
Usenet news reading and posting
SSL over POP3, SMTP, IMAP4rev1 and NNTP protocols
GnuPG support (with GPGME)
User-defined headers
Colour labels
UNIX mailspool support
Multiple MH folder support
Mbox import/export
External editor
Message queueing and drafting
Automated mail checking
Line-wrapping
Clickable URIs
Addressbook
Printing

More features

Claws Mail also includes a lot of useful and powerful features, only some of which are listed below:
Plugin mechanism (see below)
Actions
Templates
Built-in image viewer
Face and X-Face headers support
Reply-finder
Fast message cache system
Per-folder processing mechanism
Spell checking (with enchant)
Drag'n'drop support
POP before SMTP authentication
Automatic saving of message when composing
Handling of Unix signals
Control by command-line
Built-in GDB crash handler (just in case ;-)
Customisable toolbars
Powerful Quick Search function
'Dynamic' signatures
Font configuration
Themes mechanism (see available themes)
Automatic account selection
Message scoring
Ability to hide read messages
IMAP over SSH Tunnel
IMAP: CAPABILITY support.
Return-Receipt handling
Message priority setting
'Ignore thread' option
Anti-phishing URL check
Configurable notification of new mail
7bit and 8bit encoding of attachments
NNTP: auto-mark cross-posted messages
Configurable (non-)display of images
Full coloration of messages
User-definable quotation characters
Watch marked threads
Log window
Reply to part of an email
Replied and forwarded flags
Man page and documentation
Full GnuPG support
'On-the-fly' changing of the type of GnuPG encryption and/or signing used (MIME/ascii) in the Compose window
Manual selection of MIME type and encoding for attachments
Save all attachments in a mail at once
Save 2 or more selected files to a single file
SSL certificate management
User-definable newsgroup names abbreviation length
Address book: import from LDIF, Mutt or Pine natively
Address book: import from other mailers via scripts
Auto-completion of recipients (also via LDAP)
Harvest addresses for addressbook
Addressbook export to various formats
Per-folder properties:
Return-receipt
Save messages
Default To:
Subject simplification
Folder CHMOD
Default account
Folder colour
Offline synchronisation
Default dictionary

Plugins

See the Plugins page for a full list of plugins.