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Squirrelmail logo.png
Screenshot of the SquirrelMail message view
Original author(s) Nathan and Luke Ehresman[1]
Developer(s) The SquirrelMail Project Team
Initial release 14 December 1999; 15 years ago (1999-12-14)[2]
Stable release 1.4.22 (12 July 2011; 3 years ago (2011-07-12)) [±]
Preview release 1.5.2 / 17 August 2012; 2 years ago (2012-08-17)
Development status Active
Written in PHP, C
Operating system Linux, OS X, Windows, etc.
Platform Web platform
Available in More than 50 languages[3]
Type Webmail
License GNU General Public License v2
Website www.squirrelmail.org

SquirrelMail is a project that provides both a web-based email client and a proxy server for the IMAP protocol.

The webmail portion of the project was started by Nathan and Luke Ehresman[1] in 1999 and is written in PHP. SquirrelMail can be employed in conjunction with a LAMP "stack", and any other operating systems that support PHP are supported as well. The web server needs access to the IMAP server hosting the email and to an SMTP server to be able to send mails.[4]

SquirrelMail webmail outputs valid HTML 4.0 for its presentation, making it compatible with a majority of current web browsers. SquirrelMail webmail uses a plugin architecture to accommodate additional features around the core application, and over 200 plugins are available on the SquirrelMail website[5][6]

The SquirrelMail IMAP proxy server product was created in 2002 by Dave McMurtrie while at the University of Pittsburgh (where it was named "up-imapproxy", although it has become more commonly known as "imapproxy") and adopted by the SquirrelMail team in 2010.[7] It is written in C and is primarily made to provide stateful connections for stateless webmail client software to an IMAP server, thus avoiding new IMAP logins for every client action and in some cases significantly improving webmail performance.

Both SquirrelMail products are free and open-source software subject to the terms of the GNU General Public License (GPL) version 2.

The webmail product is currently available in over 50 languages.[3] SquirrelMail webmail is included in the repositories of many major GNU/Linux distributions[8][9][10][11][12][13][14][15][16] and is independently downloaded by tens of thousands of people every month.[17]


SquirrelMail webmail is available for any platform supporting PHP. Most commonly used platforms include Linux, FreeBSD, OS X and the server variants of Microsoft Windows.

SquirrelMail IMAP Proxy compiles on most flavors of Unix, and can generally be used on the same platforms as the webmail product can be with the exception of Microsoft Windows, unless used in a Cygwin or similar environment.

Future development[edit]

New releases of the stable SquirrelMail product are made as needed to address any bugs or security issues which may be discovered. Development of new features and enhancements is concentrated on the development product, which, in time, will itself become the stable product. The SquirrelMail 1.5 Roadmap outlines some of the features slated for the next developmental release, including:

  • A templating system
  • A RPC interface for use by other applications as well as AJAX-enabled SquirrelMail template sets (skins)
  • A new initialization system
  • Faster login times due to improved message header caching
  • Security enhancements, such as HTTPOnly cookies
  • Improved usability/accessibility


The SquirrelMail webmail client itself is a complete webmail system, but extra features are available in the form of plugins. A plugin allows non-standard features to be added to SquirrelMail, often without the need to modify the source code. There are over 200 third-party plugins available for download from the SquirrelMail website,[5] and SquirrelMail ships with several "standard" or "core" plugins, allowing an administrator to add:

  • Spell checking (squirrelspell)
  • Mail filters (filters)
  • Web-based administration of SquirrelMail (administrator)
  • A calendar (calendar)
  • An interface to submit bug reports semi-automatically (bug_report)

Examples of functionalities added by various third-party plugins include:

  • Address book/contact grouping and other address book expansions
  • Monitoring and security tools to track usage, fight attackers and improve security
  • Password change
  • Single sign-on support, one-time passwords, login aliases and several other credential manipulations and lookups
  • Quota reporting
  • Rich text (HTML) email composition and display
  • User-configurable front-ends for autoresponders, spam filtering systems such as SpamAssassin and server-side mail filters
  • Weather reporting
  • User account control panel


SquirrelMail webmail has been translated into over 50 languages including Arabic, Chinese, French, German, and Spanish.[3]

Notable installations[edit]

SquirrelMail has been implemented as the official email system of the Prime Minister's Office of the Republic of India for its security advantages over Microsoft's Outlook Express.[18][19][20][21]

HEC Montréal deployed SquirrelMail as part of a comprehensive webmail solution, to support thousands of users.[22]


There are several mailing lists available.[23] Several of the developers are available for live chat on IRC. A bug tracking system is available for reporting bugs or submitting patches.[23] For administrators or companies official and third party commercial support is available.

Apple shipped SquirrelMail as their supported web mail solution in Mac OS X Server.[24]

Skipped 1.4.14 version[edit]

On 27 May 2008 the SquirrelMail Team announced that, while the latest released version of their software was 1.4.13, a spammer was sending unsolicited email messages to various recipients about a 1.4.14-rc1 release candidate version which didn't really exist. The messages (usually titled "Internet Users Email Upgrade (IUEU)") urged recipients to upgrade immediately (because of supposed security issues) and contained a web link for users to do so. However, that web link pointed to a page where the spammer was collecting email addresses and passwords. Beside the fact that end users are not responsible for upgrading such software, that the "upgrade" page was merely a mock SquirrelMail login page made it clear that this was a Phishing attack. The "upgrade" page has been hosted on various compromised systems across the Internet and the attack has continued at least through July 2009 (sample).

As a result, the SquirrelMail team skipped version 1.4.14 and its next release after 1.4.13 was 1.4.15.[25]

This versioning tactic was of limited effectiveness, as later phish runs referenced 1.4.15 instead of 1.4.14.[26]

See also[edit]


  1. ^ a b "SquirrelMail history". Squirrelmail.org. Retrieved 2009-08-11. 
  2. ^ "Squirrelmail ChangeLog". Retrieved 2009-12-13. 
  3. ^ a b c "SquirrelMail translation statistics". L10n-stats.squirrelmail.org. 16 June 2009. Retrieved 2009-08-11. 
  4. ^ "SquirrelMail, a Web-Based Mail Server – O'Reilly Media". onlamp.com. Retrieved 2010-07-29. 
  5. ^ a b "SquirrelMail plugins". Squirrelmail.org. Retrieved 2009-08-11. 
  6. ^ Wallen, Jack (7 August 2007). "SolutionBase: Taking SquirrelMail to new levels". Articles.techrepublic.com.com. Retrieved 2010-10-31. 
  7. ^ "IMAP Proxy home page". Retrieved 2010-11-15. 
  8. ^ "Fedora Package Database – squirrelmail". fedoraproject.org. Retrieved 2010-03-06. 
  9. ^ "Novell: openSUSE 10.3: squirrelmail". novell.com. Retrieved 2010-03-06. 
  10. ^ "Debian – Package Search Results – squirrelmail". debian.org. Retrieved 2010-03-06. 
  11. ^ "CentOS Package List". centos.org. Retrieved 2010-03-06. 
  12. ^ "CentOS SquirrelMail Package". centos.org. Retrieved 2010-03-06. [dead link]
  13. ^ "Ubuntu – Package Search Results – squirrelmail". ubuntu.com. Retrieved 2010-03-06. 
  14. ^ "Gentoo Packages /package/mail-client/squirrelmail". gentoo.org. Retrieved 2010-03-06. 
  15. ^ "FreeBSD Ports Search – squirrelmail". freebsd.org. Retrieved 2010-03-06. 
  16. ^ "Port description for mail/squirrelmail". freebsd.org. Retrieved 2010-03-06. 
  17. ^ "Project Statistics for SquirrelMail". sourceforge.net. Retrieved 2010-03-06. 
  18. ^ "Microsoft dumped after India PM's emails go AWOL". theregister.co.uk. 17 March 2009. Retrieved 2010-03-06. 
  19. ^ "PMO's email system infected for three months". The Times of India. 15 March 2009. Retrieved 2010-03-06. 
  20. ^ "Indian PM Abandons Outlook for Open-Source Email". infopackets.com. 20 March 2009. Retrieved 2010-03-06. 
  21. ^ "No Microsoft mail for PM". techgoss.com. 16 March 2009. Retrieved 2010-03-06. 
  22. ^ "HEC Montréal: Deployment of a Large-Scale Mail Installation". linuxjournal.com. 1 May 2004. Retrieved 2010-07-25. 
  23. ^ a b "SquirrelMail support". Squirrelmail.org. Retrieved 2009-08-11. 
  24. ^ "Peachpit: Mac OS X Server Mail Service Boot Camp: Advanced Mailing List Features and Web Mail". 13 October 2006. Retrieved 2010-08-30. 
  25. ^ "Squirrelmail homepage". Retrieved 2008-10-16. 
  26. ^ "Scamdex sample". 

External links[edit]