The advantages of running Linux are well known - lower costs, better adherence to open standards, no domineering corporate power, better security, etc. However, there's one area where Linux users are subject to all the same challenges and pitfalls as other systems: corporate e-mail. E-mail remains the single biggest source of security breaches and IT headaches simply because most Linux-based IT departments still rely on Microsoft Exchange Server for their e-mail. And, because Microsoft Exchange Server has such a large installed user base, it remains a favorite target of hackers and spammers.