Comparison of email clients

The following tables compare general and technical information for a number of e-mail client programs. Please see the individual products articles for further information. This article is not all-inclusive or necessarily up-to-date.

General

Basic general information about the clients: creator/company, license/price etc.

e-mail program	Creator	Cost (USD)	Software license
Citadel	citadel.org	Free	GPL
Eudora	Qualcomm	Free (Light), Free (Pro, with ads), $20 (Pro)	Proprietary *Next release will be based upon Mozilla Thunderbird
Gnus	Gnus team	Free	GPL
GroupWise	Novell	Included with GroupWise mailbox license	Proprietary
Lotus Notes	Lotus Software / IBM	online pricelist	Proprietary
KMail	KDE	Free	GPL
Mail	Apple Computer	Part of Mac OS X	Proprietary
Mozilla Mail & Newsgroups	Mozilla Foundation	Free, part of Mozilla Application Suite	MPL, MPL/GPL/LGPL tri-license
Mozilla Thunderbird	Mozilla Foundation	Free	MPL, MPL/GPL/LGPL tri-license
Microsoft Office Outlook	Microsoft	Part of Microsoft Office, $109 stand-alone	Proprietary
Mulberry	Cyrus Daboo (previously Cyrusoft International, Inc./ISAMET	Free (as of version 4.0.5)	Proprietary
Mutt	Michael Elkins	Free	GPL
Novell Evolution	Ximian	Free	GPL
Open-Xchange	Open-Xchange	Free	GPL
Opera Mail	Opera Software	Free, Part of Opera	Proprietary
Outlook Express	Microsoft	Part of Microsoft Windows	Proprietary
Pegasus Mail	David Harris	Free	Proprietary
Pine	University of Washington	Free	Pine License
PC Pine	University of Washington	Free	Pine License
i.Scribe / InScribe	Memecode	Free/$20	Proprietary
SeaMonkey Mail & Newsgroups	SeaMonkey Council	Free, part of SeaMonkey	MPL, MPL/GPL/LGPL tri-license
Sylpheed	Hiroyuki Yamamoto	Free	GPL/LGPL
Sylpheed Claws	Sylpheed Claws team	Free	GPL
The Bat!	RitLabs	$45	Proprietary
Windows Live Mail Desktop	Microsoft	Free Adware	Proprietary
Zimbra	Zimbra	Free	MPL

Release history

A brief overview of the release history.

Client	First public release		First stable release		Latest stable release		Latest testing release
	Date	Version	Date	Version	Date	Version	Date	Version
Citadel	1987	?	1988	1.00	December 2005	6.61	?	?
Eudora	1996	?	1988	?	October 11 2006	7.1	?	?
Lotus Notes	1989	1.0	1989	1.0	September 29 2006	7.0.2	September 25 2006	7.0.2 Mac Beta 1
KMail	?	?	?	?	January 31 2006	1.9.1	?	?
Mail	?	?	?	?	June 27 2006	2.1 (752/752.2)	?	?
Mozilla Mail & Newsgroups	December 7 1998	"Preview"	March 19 1999	M3	April 21 2006	1.7.13
Mozilla Thunderbird	July 28 2003	0.1	December 7 2004	1.0	November 8 2006	1.5.0.8	July 27 2006	2.0a1
Microsoft Office Outlook	1997	97	1997	97	?	11.8010.6568 (2003SP2)	May 23 2006	12.0.4407.1004 (2007 Beta 2 Technical Refresh)
Mulberry	September 20 1996	1.0	September 20 1996	1.0	September 20 2006	4.0.6	?	?
Mutt	1995	?	?	?	July 14 2006	1.4.2.2	July 14 2006	1.5.12
Novell Evolution	11 May 2000	0.0	3 December 2001	1.0	21 November 2006	2.8.2.1	6 November 2006	2.9.2
Open-Xchange	?	?	?	?	April 2006	0.8.2	?	?
Opera Mail	September 1996	2.1b1	December 1996	2.1	September 21 2006	9.02	?	?
Outlook Express	1996	3.0	?	?	October 25 2001	6.0	?	?
Pegasus Mail	1990	?	1990	?	July 16 2006	4.41	?	?
Pine	January 15 1992	2.00	?	?	September 28 2005	4.64	?	?
i.Scribe/InScribe	1999	1.00	?	?	November 2005	1.88	December 2005	1.89
SeaMonkey Mail & Newsgroups	September 15 2005	1.0a	January 30 2006	1.0	November 8 2006	1.0.6	November 8 2006	1.1b
Sylpheed	January 2000	0.1.0	December 2004	1.0.0	February 13 2006	2.2.0	?	?
Sylpheed Claws	May 2001	0.4.67	January 2005	1.0.0	June 20 2006	2.3.1	?	?
The Bat!	March 1997	1.0 Beta	March 1998	1.00 Build 1310	September 4 2006	3.85	December 2 2006	3.86.08
Windows Live Mail Desktop	?	?	?	?	?	?	July 2006	8.0.0783
Zimbra	?	?	?	?	April 2006	3.1	?	?

Operating system support

The operating systems on which the clients can run natively (without emulation).

	Microsoft Windows	Mac OS X	Linux	BSD	Unix
Citadel	No	Yes	Yes	Yes	Yes
Eudora	Yes	Yes	No	No	No
Gnus	Yes	Yes	Yes	Yes	Yes
Lotus Notes	Yes	Yes	Yes	No	No
KMail	No	Yes	Yes	Yes	Yes
Mail	No	Yes	No	No	No
Mozilla Mail & Newsgroups	Terminated (1.7.13)	Terminated (1.7.13)	Terminated (1.7.13)	Terminated (1.7.13)	Terminated (1.7.13)
Mozilla Thunderbird	Yes	Yes	Yes	Yes	Yes
Microsoft Office Outlook	Yes	Yes (Microsoft Entourage)	No	No	No
Mulberry	Yes	Yes	Yes	Yes	Yes
Mutt	Yes	Yes	Yes	Yes	Yes
Netscape Messenger	Terminated (4.80)	Terminated (4.80)	Terminated (4.80)	Terminated (4.80)	Terminated (4.80)
Novell Evolution	Yes (alpha)	Yes	Yes	Yes	Yes
Opera Mail	Yes	Yes	Yes	Yes	Yes
Outlook Express	Yes	No	No	No	No
Pegasus Mail	Yes	No	No	No	No
Pine	Yes	Yes	Yes	Yes	Yes
i.Scribe/InScribe	Yes	No (Port in progress)	Yes	No	No
SeaMonkey Mail & Newsgroups	Yes	Yes	Yes	Yes	Yes
Sylpheed	Yes	Yes	Yes	Yes	Yes
Sylpheed Claws	Yes	Yes	Yes	Yes	Yes
The Bat!	Yes	No	No	No	No
Windows Live Mail Desktop	Yes	No	No	No	No
Zimbra	Yes	Yes	Yes	Yes	Yes

Protocol Support

What e-mail and related protocols and standards are supported by each client.

Client	POP3	IMAP4	SMTP	NNTP	LDAP		IMSP	ACAP	Feeds				iCalendar
					v2	v3			RSS 0.91	RSS 1.0	RSS 2.0	ATOM
Eudora	Yes	Yes	Yes	No	Yes	Yes	No	Yes	No	No	No	No	No
Mail	Yes	Yes	Yes	No	?	?	?	?	No	No	No	No	No
Gnus	Yes	Yes	Yes	Yes					Yes	Yes	Yes	No
KMail	Yes	Yes	Yes	No Template:Refun	Yes		?	?	No Template:Refun	No Template:Refun	No Template:Refun	No Template:Refun	No Template:Refun
Lotus Notes	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes Template:Refun	Yes	Yes	Yes	Yes
Mozilla Thunderbird	Yes	Yes	Yes	Yes	Partial		?	No	Yes			Yes	Yes (with extension)
Mulberry	Yes	Yes	Yes	Yes	Yes		Yes	Yes	No	No	No	No	Yes
Mutt	Yes	Yes	No (uses sendmail)	No (slrn looks alike)	Partial (resolve real names through NSS)		?	?	No	No	No	No	No
Opera Mail	Yes	Yes	Yes	Yes	No	No	?	?	Yes	Yes	Yes	Yes	No
Microsoft Office Outlook	Yes	Yes	Yes	No	Yes		?	?	No	No	No	No	No
Novell Evolution	Yes	Yes	Yes	Yes	?	?	?	?	No	No	No	No	Yes
Outlook Express	Yes	Yes	Yes	Yes	Template:But yes		?	?	No	No	No	No	No
Pegasus Mail	Yes	Yes	Yes		Yes
Pine	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No
i.Scribe/InScribe	Yes	Yes	Yes	No	Yes (Plugin required)	Yes (Plugin required)	No	No	No	No	No	No	No
Sylpheed Claws	Yes	Yes	Yes	Yes	Yes		?	?	No	Yes (RSSyl plugin required)	Yes (RSSyl plugin required)	Yes (RSSyl plugin required)	Yes (vCalendar plugin required)
TheBat!	Yes	Yes	Yes	Yes (MyGate plugin required)	Yes	No	No	No	Yes (plugin rss2mail or rss2pop3 required)	Yes (plugin rss2mail or rss2pop3 required)	Yes (plugin rss2mail or rss2pop3 required)	Yes (plugin rss2mail or rss2pop3 required)	No
Windows Live Mail Desktop	Yes	Yes	Yes	Yes	Yes				Yes	Yes	Yes	Yes	No
Zimbra	Yes	Yes	?	?	?	?	?	?	?	?	?	?	?

• ^ KDE supports Newsgroups (NNTP) by the use of KNode
• ^ KDE supports feeds by the use of Akregator
• ^ KDE supports iCal by the use of KOrganizer
• ^ Studio Blog Reader is one RSS reader application for Lotus Notes.

Authentication Support

Client	Regular		MSN (NTLM) browser login	Compuserve (RPA)	MD5 APOP Template:Refun	CRAM-HMAC Template:Refun			DIGEST-MD5	with hardware token PKCS #11	Biometric	SMTP Auth Template:Refun	SSL/TLS Client Certificate
	LOGIN	PLAIN				MD5	SHA1	RIPEMD
Eudora	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	Yes
MailTemplate:Refun	?	?	?	?	?	Yes	?	?	?	?	?	Yes
Gnus	?	?	?	?	?	?	?	?	?	?	?	?
KMail	Yes	Yes	Yes	No	Yes	Yes	No	No	Yes	No	No	No
Lotus Notes	Yes		Yes	No	No	No				Yes	No	Yes
Mozilla Thunderbird	Yes	Yes	Yes	No	Yes	Yes	No	No	No [1]	No	No	Yes
Mulberry	Yes	Yes	Yes	No	No	Yes	No	No	Yes	No	No	Yes	Yes
Mutt
Novell Evolution	Yes	Yes	Yes	No	Yes	Yes	No	No	Yes	No	No	Yes
Opera Mail	Yes	Yes	No	No	Yes	Yes	No	No	No	No	No	Yes
Microsoft Office Outlook	Yes	No	Yes	No	No	No	No	No	No	No	No	No
Outlook Express	Yes	No	Yes	No	No	No	No	No	No	No	No	Yes
Pegasus Mail
Pine	Yes		No	No	No	Yes				No	No	Yes
i.Scribe / InScribe	Yes	Yes	Yes	No	Yes	Yes	No	No	Yes	No	No	Yes	No
Sylpheed Claws	Yes				Yes	No						Yes
TheBat!	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	Yes	Yes	Yes
Windows Live Mail Desktop	Yes	No	Yes	No	No	No	No	No	No	No	No	No
Zimbra	?	?	?	?	?	?	?	?	?	?	?	?

• ^ Description: RFC-2554
• ^ Description: RFC-1734
• ^ Description: RFC-2195
• ^ 10.1.3 Apple adds SSL and CRAM-MD5 support to Mail

SSL and TLS Support

Client	Secure POP3		Secure IMAP4		Secure SMTP		Secure NNTP		Secure LDAP		OCSP Template:Refun	CRL Template:Refun
	SSL	TLS Template:Refun	SSL	TLS Template:Refun	SSL	TLS Template:Refun	SSL	TLS	SSL	TLS
Eudora	Yes	Yes	Yes	Yes	Yes	Yes	No	No	Yes	Yes
Mail	Yes	?	Yes	Yes	Yes	?	No	No	Yes	?
Gnus	?	?	?	?	?	?	?	?	?	?
KMail	Yes	Yes	Yes	Yes	Yes	Yes	No	No
Lotus Notes	Yes		Yes		Yes	Yes	Yes		Yes			Yes
Mozilla Thunderbird	Yes	Yes	Yes	Yes	Yes	Yes	Yes		Yes		Yes	Yes
Mulberry
Mutt
Novell Evolution	Yes	Yes	Yes	Yes	Yes	Yes	No	No	?	?
Opera Mail	Yes	Partial Template:Refun	Yes	Partial Template:Refun	Yes	Partial Template:Refun	Yes	No	No	No
Microsoft Office Outlook	Yes	No	Yes	No	Yes	No
Outlook Express	Yes	No	Yes	No	Yes	No
Pegasus Mail	Yes		Yes		Yes				Yes
Pine	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	No
i.Scribe / InScribe	Yes	Yes	Yes	Yes	Yes	Yes	n/a	n/a	No	No	n/a	n/a
Sylpheed Claws	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
TheBat!	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No	No	No	No
Windows Live Mail Desktop	Yes	No	Yes	No	Yes	No	?	?	?	?
Zimbra	?	?	?	?	?	?	?	?	?	?

• ^ Description: RFC-2487
• ^ Description: RFC-2595
• ^ Opera Mail does not support STARTTLS command on special ports, like 995 for pop3 connection
• ^ Online Certificate Status Protocol - Description: RFC-2560
• ^ Certificate Revocation List - Description: RFC-3280

Features

Information on what features each of the clients support.

Note that for all of these clients, the concept of "HTML support" does not mean that they can process the full range of HTML that a web browser can handle. Almost all email readers limit HTML features, either for security reasons, or because of the nature of the interface. CSS and and Javascript can be especially problematic. A number of articles describe these limitations per-email-client; see 1, 2, 3, and 4

Client	HTML e-mail	UTF-8 support	Image blocking	Junk filtering		Thread view	PGP support	S/MIME support
				local	server-side			protocol	OCSP	CRL	certificates on tokens, smartcards support
Citadel	Yes	Yes	No	Yes (plugs into SpamAssassin)		No
Eudora	Yes	No	Yes	Yes (Pro only)		Yes		Yes
Gnus	Yes	Yes	Yes	Yes		Yes	Yes	Yes
Lotus Notes	Yes	Yes	Yes	Yes	Yes	Yes Template:Refun	Yes	Yes		Yes	Yes
KMail	Yes	Yes	Yes	Yes		Yes	Yes (GPG)	Yes
Mail	Yes	Yes	Yes	Yes		Yes	Yes (with the GPGMail-plugin	Yes
Mozilla Thunderbird	Yes	Yes	Yes	Yes (Phishing filter added in 1.5.0.4)	No	Yes	Yes (with Enigmail)	Yes
Mulberry	Yes		Yes	No		Yes	Yes Template:Refun	Yes Template:Refun
Mutt	Partial Template:Refun	Yes	Yes (no support for images)	Yes		Yes	Yes	Yes
Novell Evolution	Yes	Yes	Yes	Yes		Yes	Yes	Yes
Opera Mail	Partial Template:Refun	Yes	Yes	Yes		Yes	No	No
Microsoft Office Outlook	Yes	Yes	Yes	Yes		Yes		Yes
Outlook Express	Yes	Yes	Yes	No		Yes	Yes	Yes
Pegasus Mail	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Pine	Partial Template:Refun	Yes	Yes	No		Yes		Yes
i.Scribe / InScribe	Partial Template:Refun	Yes	Yes	Yes	No	Yes	Yes (plugin for GnuPG required)	No	No	No	No
SeaMonkey Mail & Newsgroups	Yes	Yes	Yes	Yes		Yes	Yes (with Enigmail)	Yes
Sylpheed	No	Yes	Yes	Yes		Yes
Sylpheed Claws	Partial Template:Refun	Yes	Yes	Yes		Yes	Yes	Yes
The Bat!	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Partial Template:Refun	Partial Template:Refun	Yes Template:Refun
Windows Live Mail Desktop	Yes	Yes	Yes	Yes (Phishing filter also included)		Yes	Yes	Yes
Zimbra	Yes	Yes	Yes	Yes		Yes	?	?
Client	HTML e-mail	UTF-8 support	Image blocking	Junk filtering		Thread view	PGP support	S/MIME support
				local	server-side			protocol	OCSP	CRL	certificates on tokens, smartcards support

• ^ HTML handling is read-only (cannot compose HTML e-mails).
• ^ First release 6.0 (September 2003), enhancements introduced in release 7.0 (August 2005)
• ^ PGP/GPG and S/MIME support require a free (included) plugin.
• ^ The Bat! supports two modes of S/MIME: Internal Implementation and via Microsoft Crypto API. CRLs and OCSP are only supported in the latter mode.
• ^ The Bat! supports two modes of S/MIME: Internal Implementation and via Microsoft Crypto API. Internal implementation only supports eToken and iKey10xx tokens and can import certificates (from PKCS#12/PFX format) which were created outside The Bat!. CryptoAPI supports any kind of tokens and smart cards which have a corresponding Cryptographic Service Provider installed.

Messages features

Client	Label Messages				Spell Checking	Signatures	Native images preview
	with Colors	with flag	antidelete	add note			jpeg	gif	bmp	png	others
Citadel
Eudora	Yes	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes
IBM Lotus Notes	Yes	Yes			Yes	Yes	Yes	Yes	Yes
KMail	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Mail	Yes	Yes			Yes	Yes	Yes	Yes	Yes	Yes	Yes
Mozilla Thunderbird	Yes	Yes			Yes (with extension)	Yes	Yes	Yes	Yes	Yes	ico
Mulberry		Yes			Yes	Yes	No	No	No	No	No
Mutt
Novell Evolution	Yes	Yes			Yes	Yes	Yes	Yes	Yes	Yes
Opera Mail					Yes Template:Refun	Yes	Yes	Yes	Yes	Yes
Microsoft Outlook
Outlook Express
Pegasus Mail					Yes
Pine
i.Scribe / InScribe	Yes	No	No	Yes	Yes (with plugin)	Yes	Yes (with libjpeg)	Yes	Yes	Yes (with libpng)	Yes
SeaMonkey Mail & Newsgroups
Sylpheed
Sylpheed Claws	Yes	Yes	No	No	Yes	Yes	Yes	Yes		Yes
The Bat!	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Windows Live Mail Desktop
Zimbra
Client	Label Messages				Spell Checking	Signatures	Native images preview
	with Colors	with flag	antidelete	add note			jpeg	gif	bmp	png	others

• ^ Opera supports full integration with GNU Aspell, which is its requirement for spell checking.

Database, folders and customization

Client	Encrypted database	Virtual folders	Scheduled backup	Ticker notification	Customizable interface	Customizable keybindings	Fragmented attachments	Database search with regular expressions support	Indexed search	Search folders Template:Refun	IMAP search
Citadel
Eudora	No	Yes	No	No	Yes	Yes	Yes	Yes	Yes	No	Yes
Lotus Notes	Yes	Yes	Yes	Yes	Yes	Yes	Yes (called truncated document)	Yes	Yes
KMail	No	No	No	Yes	Yes	Yes	No			Yes
Mail		Yes							Yes (with Spotlight OSX 10.4)
Mozilla Thunderbird		Yes							No	Yes	Yes
Mulberry	Template:Refun	Template:Refun	Template:Refun		Yes			Yes
Mutt	?	?	?	?	Yes	Yes
Novell Evolution	No	Yes	?	No	Partial	Yes Template:Refun	Yes	No	?	Yes	Yes
Opera Mail	No	Yes (all folders are virtual)	No	Yes	Yes	Yes	No			Yes
Microsoft Office Outlook	No (when Best Encryption is used, .pst file cannot be read by a hex editor)	Yes	Yes	Yes	Yes				Yes (in beta)	Yes
Outlook Express	No	No	No	No	No	No	Yes		No
Pegasus Mail
Pine
i.Scribe/InScribe	No	No	No	No	Yes	No	No	No	No	No	No
SeaMonkey Mail & Newsgroups											Yes
Sylpheed
Sylpheed Claws	No	No	No	No	Yes	Yes
The Bat!	Yes (RC2 128 bit) (with Pro and Voyager version)	Yes	Yes	Yes	Yes	Yes	Yes	Yes (PCRE 6.2)	No	Yes	Yes
Windows Live Mail Desktop	No	No	No	No	Yes	No	Yes		Yes
Zimbra	?	?	?	?	?	?	?
Client	Encrypted database	Virtual folders	Scheduled backup	Ticker notification	Customized interface	Customizable keybindings	Fragmented attachments	Database search with regular expressions support	Indexed search	Search folders Template:Refun	IMAP search

• ^ Mulberry is a dedicated IMAP client; If the IMAP server has these ablities, Mulberry can use them.
• ^ Search Folders are virtual folders that contain views of all e-mail items matching specific search criteria. Search Folders display the results of previously defined search queries.
• ^ Editable keybindings is part of GNOME, provided "Editable menu accelerators" is enabled in GNOME's "Menus & Toolbars" control applet.

Templates, scripts and programming languages

Client	Message templates				Support in message templates scripts, programming languages
	new	reply	forward	read confirmation	PascalScript	JavaScript	VBScript	PHP Scripts	Python	Regular Expressions
Citadel
Eudora	Yes	Yes	Yes	Yes	No	No	No	No	No
i.Scribe / InScribe	Yes	Yes	Yes	No	No	Yes	No	No	No	No
KMail
Lotus Notes	Yes	Yes	Yes	Yes	No	Yes	No	No	No
Mail
Mozilla Thunderbird
Microsoft Office Outlook	Yes	Yes	Yes	Yes
Mulberry	Yes	Yes	Yes	Yes	No	No	No	No	No
Mutt
Novell Evolution	Yes	Yes	Yes	Yes	?	?	?	?	?	?
Opera Mail					No	No	No	No	No
Outlook Express	Yes	Yes		Yes		Yes	Yes
Pegasus Mail	Yes	Yes	Yes	Yes
Pine
SeaMonkey Mail & Newsgroups
Sylpheed
Sylpheed Claws	Yes	Yes	Yes	Yes	No	No	No	No	No
The Bat!	Yes	Yes	Yes	Yes	No	Yes (with JavaScript Macro plugin)	Yes (with plugin XMP)	Yes (with plugin XMP)	Yes (with plugin TBPyxie)	Yes (PCRE 6.2)
Windows Live Mail Desktop	Yes	Yes		Yes		Yes	Yes
Zimbra	?	?	?	?	?	?	?	?	?
Client	new	reply	forward	read confirmation	PascalScript	JavaScript	VBScript	PHP-Scripts	Python	Regular Expressions

List of e-mail clients

The following is a list of e-mail clients.

Graphical

• acme Mail - interface for upas
• Aethera
• Apple Mail
• Balsa
• Becky!
• Bloomba
• Citadel
• Claris Em@iler
• DreamMail
• Eudora
• Forté Agent
• FoxMail
• IncrediMail
• i.Scribe/InScribe
• KMail
• Lotus Notes
• Opera M2
• Microsoft Entourage
• Microsoft Office Outlook
• Outlook Express
• Mail
• Mozilla Thunderbird
• Mozilla Mail & Newsgroups
• Mulberry
• Netscape
• Novell Evolution
• Novell GroupWise
• Pegasus Mail
• SeaMonkey Mail & Newsgroups
• Sylpheed
• Sylpheed Claws
• The Bat!
• Windows Live Mail Desktop
• YAM (Yet Another Mailer)

Text-based

• Elm
• Elmo
• Gnus
• mailx(1) – one of the traditional mail(1) implementations
• MH
• Mutt
• Pine
• Upas – e-mail filesystem for Plan 9 from Bell Labs

Web-based

• 24SevenOffice
• BlogMail
• Citadel
• Horde IMP
• Hula project
• OpenWebmail
• RoundCube Webmail
• Skweezer Mail
• SquirrelMail
• Zimbra
• WebPine

Historical

• Calypso
• Windows Messaging
• Microsoft Internet Mail and News
• Netscape Communicator

See also

• Unicode and e-mail
• List of personal information managers
• Comparison of layout engines

External links

• Michigan Engineering - E-mail Client Comparison
• UAlbany ITS: Email Services - Email Choices: Mail Client Comparison Summary Tables
• E-mail client comparison
• T&B : Email : Clients (of historical interest--last updated in 1999)
• imap.org's list of products supporting IMAP
• Remail - research by The Collaborative User Experience group at IBM