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.
The association said the question was a reaction to media reports last year that several Palestinian-American travelers were asked to open their e-mail accounts and show airport security before being denied entry.