The first version of Pegasus Mail worked with Novell Netware networks. It has a mail system called “Message Handling System” (MHS) with a cut-down version called “FirstMail” bundled with NetWare. It also supports POP3, IMAP and SMTP protocols. Earlier versions used only a non-standard format for mail folders. There are also available older versions for MS-DOS and Apple Macintosh, although it is no longer developed or supported.

The Microsoft Windows version of Pegasus Mail does not use Microsoft Internet Explorer’s HTML layout engine to display HTML e-mail, which is a key feature because of its ability to reduce high-risk of infection from viewing an email. Malicious HTML is dependent on the exact target application and OS and not using the HTML format of Windows, therefore automation of commands such as ActiveX and JavaScript are not allowed to execute from within an email.

With the release of 4.41 version, the software has improved many features such as: filtering of spam with header and body checking in key phrases; improved HTML rendering engine; better support for special character encoding (especially with UTF-8), phishing protection and a full-fledged Bayesian spam filter.

Compared with other software, Pegasus Mail has minimal system requirements. The version 4.52 requires only around 13.5 MB of hard drive space, the installed program excluding mailboxes. It is also suitable as a portable application for USB drives, since Pegasus Mail does not make changes to the Windows registry or the system directory. Language packs are available other than English. It also includes improvements for Windows 7.

Pegasus Mail 4.61 was released on February 23, 2011. New improvement includes: new graphics, an updated interface, a number of changes and improvements for bug fixes, improvements to the editor and elsewhere. It also includes a new HTML renderer for built-in Windows renderer of Internet Explorer. Another alternative is BearHTML renderer.

Version 4.70 was released on March 8, 2014, which includes improvements of Hunspell for spelling check and OpenSSL for encryption.

According to David Harris, the Pegasus Mail is being continuously improved and there will be a Pegasus Mail version 5.0 that users should wait for.