Postini on Monday announced discovery capabilities with its message archiving service and also announced three new plans for the existing service.

The new Postini Message Discovery service augments the company's existing message archiving service to help customers better manage and find archived e-mail and instant messages, particularly ones related to litigation, say company officials.

The new feature is an optional add-on that can be used to manage both internal and external requests for messages. It is designed to make it easier for administrators, employees in human resources and legal, or any authorized party to quickly find messages involved in an investigation, the company says. These messages can be saved and exported or put on "litigation hold" to ensure the data is preserved.

Postini also announced new plans for customers of its message archiving service. The basic service is for customers that need online digital message archiving; the standard service adds control over storage pools and the ability for users to search the archives for messages; and the professional service provides the standard features plus "immutable" storage of message data, officials say.

Pricing information for the new discovery service and the archiving plans was not available.

Last month Google announced plans to acquire Postini for US$625 million.