SquirrelMail is a standards-based webmail package written in PHP4. It includes built-in pure PHP support for the IMAP and SMTP protocols, and all pages render in pure HTML 4.0 (with no Javascript) for maximum compatibility across browsers. SquirrelMail has all the functionality you would want from an email client, including strong MIME support, address books, folder manipulation, and multiple language support. Check out the SquirrelMail site for more info: SquirrelMail
To activate SquirrelMail on your 'Plusmail' account, you need to first activate PHP. Do this via your web control panel (http://YourDomainName.com/cgi-bin/plusmail), under the "Free Scripts" category. Once PHP is activated (about 15 minutes), then you will be able to access the SquirrelMail login page. (On the Ensim accounts, SquirrelMail is activated by default.)
To access Webmail / SquirrelMail on your account, go to http://YourDomainName.com/webmail/