Lotus supports PGP by offering its APIs to customers that want to build a plug-in for Notes.
Senders can digitally sign a message by encrypting it with their private keys.
Then the recipient can decrypt the message using the sender's published public key to validate the identity of the sender. Exchange Server 5.5, Notes 4.6 and GroupWise 5.2 support the option of encrypting messages by default or on a per-message basis. However, where a user's certificate and public keys are stored varies by product. Exchange stores both the certificate and the keys within the Exchange directory, while Notes stores the certificate within the user document, a collection of user attributes. Novell plans to store and manage X.509 certificates in NDS in the future.