BlackBerry Enterprise Server

A BlackBerry Enterprise Server, or BES for short, is software that links the BlackBerry devices of its employees to the corporate email server. Currently, a BES can support one of three email servers: Lotus Notes, Microsoft Exchange, or Novell GroupWise.

As a BES requires tight integration with the email server, it must be installed within the corporate network, inside the public firewall. (While it's possible to install a BES inside a DMZ — demilitarized zone — this is not a recommended or supported configuration.) At startup, the BES initiates a persistent outgoing connection (on port 3101) to the BlackBerry NOC (network operations center). The NOC then acts as a relay between the individual BlackBerry handhelds and the BES.

Currently, each BlackBerry handheld can only be paired with one BES. Communication between the two is secured by using private encryption keys that are generated during the pairing operation.