What is BIS?
BlackBerry Internet Service BIS, is set up on your BlackBerry. It allows you to forward your personal or business email to the handheld. Some accounts like GMAIL will also sync contacts and calendar but may not. BlackBerry Desktop Software is used to sync Calendar, Contacts, Tasks and Notes if it is not sync’d by the email provider.
What is BES?
BlackBerry Enterprise Server. It gives your BlackBerry access to a corporate email and everything is wirelessly sync’d so you do NOT need BlackBerry Desktop Software to sync. BES gives the BES administrator control over what the devices can and cannot do. For example, the BES admin may push a password policy to the device and the end user must abide by it. There are over 500 policies that can be pushed.
In conclusion (from CrackBerry)
BIS provides a direct link between your phone and your wireless provider, but after that all traffic essentially goes out over the Internet. Any and all security becomes the responsibility of the BlackBerry application in question, so there are no security guarantees. That said, BIS does a good job at providing Internet and email support and, best of all-- you don’t have to set anything up.
BES provides what is essentially a direct link between your phone and your office environment. It’s very secure, flexible, and gives your company control over all aspects of the BlackBerry. There is a certain ‘baseline’ security inherent in all data transactions, and your IT department can always disable your BlackBerry if it’s been compromised.
Smaller companies, or individuals, are well served by BIS—it provides you with almost everything you need. Larger organizations, with their own internal mail systems and other infrastructure, should definitely be using BES.