SquirrelMail is a webmail package written in PHP4. This standards-based software includes built-in pure PHP support along with IMAP and SMTP protocols.

The SquirrelMail software was developed aiming to access e-mail and address books effectively through a web interface from anywhere in the world. After a thorough research on several open source web mail packages, SquirrelMail appeared in the market with customizable look and feel along with satisfying users requirements.

The pages of SquirrelMail are created in pure HTML for providing maximum compatibility across different browsers. No JavaScript were required for it. However, it has strong MIME support and comes with a flexible plugin system.
Apart from these SquirrelMail consists of all the functionalities that an ideal e-mail client should have like address books, folder manipulation etc.

SquirrelMail webmail package is very easy to configure and install. It runs best on UNIX or Linux platforms. However, it also works well on Windows operating system. Other requirements for running SquirrelMail are:
· IMAPrev1 server like uw-imap, courier-imap, CommuniGate, MercuryMail 32 etc.
· Web Server with PHP4 installed (Squirrelmail doesn’t work with PHP5)
· Perl installed on the system
· Aspell installed if using SquirrelSpell plugin
· PHP with gettext and mbsupport
· Imap server for supporting sort and thread imap extension
· Cookies must be enabled in the users browsers

The SquirrelMail Project takes security very seriously. Any security related issues are resolved by Squirrelmail development and management team if found and reported them.