Patent ID: 8667266

Claim:
A device comprising a processor and memory, wherein the processor is configured to: identify a distribution list address in a message; determine one or more member addresses associated with the distribution list address; for each of the one or more member addresses, determine if a public key for a member identified by the member address is available on the device; if a public key for a member address is not available on the device, search for a certificate comprising a public key for the member address, from one or more certificate servers; if a certificate for the member address is found, retrieve the certificate from the certificate server and store it on the device; for each member whose public key is available on the device, encrypt the message to the member using the public key for the member; if each of the one or more member addresses associated with the distribution list identifies a member whose public key is available on the device, send the encrypted message to the distribution list address without replacing the distribution list address with member addresses; and if not all of the one or more member addresses associated with the distribution list identify a member whose public key is available on the device, replace the distribution list address with one or more member addresses that identify members whose public key is available on the device but not with any member addresses that do not identify members whose public key is available on the device, and send the encrypted message to each member address that identifies a member whose public key is available on the device.