First, the mail accounts are something you need to configure on your Exchange (mail) server. The mail accounts and e-mail software has nothing to do with actually accessing the network wirelessly or not.

A connection is a connection whether wired or not. As long as the mail accounts are configured correctly on the mail server, and the e-mail software is setup to check mail with the correct username/password on the correct server you're set that far.

As for the wireless network itself, there are several easy, built in, ways to keep the casual “war driver” or park bench surfer out of your wireless network while letting your "car driving" users in.

The sad things is, so few network admins take the time to even attempt to enable them because it may take some effort. Get familiar with the following functions of your wireless router:

** WEP encryption - WEP is breakable for someone with the right tools and time, BUT many times it's enough to make people move on to much easier targets. Take the time to read up on it in your router configuration and documentation. Configure it on the router and the laptops that will be accessing the network from the cars.

** SSIDs - SSIDs broadcasts the name of and other information about your network to anyone who happens by with a wireless card. Leaving this on makes it easier for wireless clients to connect automatically without configuration, but it also allows anyone to learn some basic things about your network. Bad stuff, DISABLE this on your router if you don't have to have it on.

** Default SSID network ID name & router passwords - Two words, change them! It is way too easy to find default network names and router passwords online. If you don't change your defaults, you allowing anyone to access your network with minimal effort. Take the two seconds to make the changes and you'll be glad you did.

** MAC address filtering - I've found this to be the most overlooked security feature of a wireless network. MAC address filtering allows you maintain a list of NIC card MAC addresses that are approved for accessing the wireless network. In theory, any packets sent from an unapproved MAC address are dropped and not allowed access to the network.

While filtering MAC address access on your wireless network may become pretty labor intensive (you may have to manually maintain a list of your companies NIC card MAC addresses), I believe it's well worth it. Since you only have 5 computers that will be accessing the wireless network from outside, this should be a really painless thing to do.

And yes, MAC addresses can be spoofed so this isn't a fool proof, but MAC address filtering can add one more layer of deterrence when combined with WEP, disabling SSIDs, and changing default router/access point passwords.