BlackBerry Internet Service Encryption (BIS)
All the Email communications between BlackBerry Internet services & its subscriber’s Smartphones are not encrypted (as per popular belief). Especially when there is communication through wireless network they are encrypted using the wireless carrier security model. In short the only safeguard is what the carrier is providing you by encrypting its wireless traffic by means of typical 2G or 3G protocols.
Your wireless carrier can give government agencies access to your traffic providing the power to look at your communication easily. RIM has even admitted that they can provide such wiretap as per court order since there was no encryption at the first place so they would not decrypt the traffic.
BlackBerry Enterprise Server Encryption (BES)
You must be wondering then what exactly is encrypted on your Blackberry? If your BlackBerry Smartphone is on BlackBerry Enterprise Server ( BES ) then all the emails are either sent or received between BES server & your Smartphone is encrypted using Triple DES (3DES) or AES encryption.
If you are using BlackBerry Internet Service Encryption (BIS) Or BlackBerry Enterprise Server Encryption (BES) for emails then only emails sent through BES are encrypted
BlackBerry Messenger Encryption
BlackBerry Smartphones uses Global PIN Encryption key which helps these devices to scramble PIN messages hence all the PIN messages we receive or sent are either decrypt or encrypt on our BlackBerry devices. PIN messages are not encrypted by default instead they are scrambled using cryptographic key.