New to version 5.0 of the BlackBerry Device Software is the built-in diagnostic utility which enables you to quickly check that the device is registered with the network operator, with the RIM infrastructure and also with your corporate BES server (if you're using BES service as opposed to BIS service).
You can usually check at a glance whether your handheld device is registered with the BlackBerry service as well as simply with the network operator, by looking at the type of signal being displayed: be it GSM, GPRS, EDGE or 3G - if the characters are in lower case that is usually an indication that the unit is not registered to the BlackBerry infrastructure; capital letters indicate correct registration.
Should you want to perform more detailed diagnostics, select the Options icon from the main menu. Select the Mobile Network menu entry:

The following screen will be displayed:

Press the menu button and select the entry for Diagnostics Test. The following window will be displayed:

Press the menu button and select the Run option:

Verify that all tests are completed successfully:

• BlackBerry Registration
• Connected to BlackBerry
• BlackBerry PIN-PIN

During this test the device will attempt to send itself a PIN message via the BlackBerry infrastructure. If the PIN message is received (which will displayed in your Inbox), then the device is correctly registered with the mobile network.