The 2,600 word missive was titled "customer focus: comparing Windows with Linux and UNIX". In it, Ballmer repeated the key themes of Microsoft's Get The Facts campaign.
He claimed that Windows was a better choice than Linux in terms of security, total cost of ownership (TCO) and protection against legal action over patent violations -- charges that Linux companies were quick to challenge on Wednesday.
"As organisations increasingly rely on IT to perform mission-critical functions, and with complexity a growing challenge, choosing the right computing platform for the long term can make the difference between profit and loss, and between future success and failure," wrote Ballmer.
"And it's pretty clear that the facts show that Windows provides a lower total cost of ownership [than Linux]; the number of security vulnerabilities is lower on Windows; and Windows responsiveness on security is better than Linux; and Microsoft provides uncapped IP indemnification of their products, while no such comprehensive offering is available for Linux or open source," Ballmer added.
Gael Duval, co-founder of Mandrakesoft, believes that Ballmer's email is indicative of a change of strategy from Microsoft.