While open-source e-mail and calendaring software, such as Mozilla Thunderbird e-mail software and the Lightning calendaring plug in, is good stuff, it's not easy for a small office to set up messaging software of any kind without a bit of professional help, unless you're an office full of techies.

FORBES: Magazine Article

Mozilla offers free versions of a web browser (Firefox) and e-mail client (Thunderbird) for free.

FORBES: Don't Waste Your Time Playing the Blame Game: Who Loses When You Do? The Customer, of Course