Northern Rock has implemented email security software from supplier Symantec, in order to meet changing regulatory requirements.
The nationalised bank will implement Symantec PGP Universal Gateway Email as part of security efforts for corporate and customer data.
The bank, which has 75 UK branches as well as online and telephone banking operations, has rolled out the service to all its staff.
The system offers centrally managed, standards-based email encryption. It encrypts data at the gateway in order to protect data from unauthorised access during transit over the internet as well as at rest on Northern Rock's mail servers. It also meets UK regulatory requirements.
Rick Hunkin, chief risk officer at Northern Rock, said the bank takes "a proactive approach to data protection". But he added that "with increasing regulatory pressures, we thought the time was right to upgrade our existing security strategy".
Last month, Northern Rock announced it was cutting 650 jobs, and could not say if IT staff were safe. Last year, government auditors said that poor IT systems at the bank prevented the government from being able to wind it down when it became a casualty of the subprime mortgage crisis in 2007.