Because it is memory-based, the Cloudmark software is billed as defending against spam and malware in multiple mailboxes, rather than havIng to be set up for each account.

Known as DesktopOne, the software has entered free beta testing and installs as a toolbar on users' email clients – Cloudmark says that Outlook, Outlook Express, Windows Mail and Thunderbird 3 are currently supported.

The company says that a version for Outlook 2010 is currently in development and, because the software resides in memory, it will intercept spam and malware even when the email client is not loaded.

Infosecurity notes that this is achieved because the DesktopOne software is loaded as an icon in the Windows tray, which can be accessed using a double click.

Reaction to the free beta test has been favourable on Cloudmark forums, which reports that the software is now in version 6 of its beta code, following initial release in mid-March.

There is no word on when the software will be released commercially or how much it will cost when it is released.