Just my 2c worth; it doesnt appear to have been mentioned that for your mobile device to connect to the Exchange server when away from the company network you need to have an Internet facing mail server. If you need a VPN to connect to your mail server (i.e. you are on a private IP address range) then you wont be able to connect unless you have a VPN running on the Android device.
Many companies use Exchange in a private network, it can send and receive emails to and from other email servers but you can not use Outlook to connect to the Exchange server from outside the private network unless you use a VPN.
The BlackBerry devices can get email because the BlackBerry Enterprise Server copies email from the Exchange server to the BlackBerry network for delivery. With a Blackberry you pickup your email from BlackBerry not from your Exchange server.