Patent ID: 8019085

Claim:
A method of sending encrypted messages, wherein acts of the method are performed at a first server, the method comprising: receiving a message from a mobile communication device, wherein the message identifies a distribution list address in a header of the message; determining one or more member addresses associated with the distribution list address; for each member address, determining if a public key for a member identified by the member address is accessible by the first server; for each member whose public key is accessible by the first server, encrypting the message to the member by employing asymmetric encryption at the first server using the public key for the member; sending the encrypted message to a second server that maintains the distribution list, at the distribution list address, without replacing the distribution list address with member addresses if each of the one or more member addresses associated with the distribution list identifies at least one member whose public key is accessible by the first server; at the first server, determining that not all members identified by the one or more member addresses associated with the distribution list are able to decrypt the message, if at least one of the one or more member addresses associated with the distribution list does not identify at least one member whose public key is accessible by the first server; at the first server, expanding the distribution list address within the header of the message only after determining that not all members identified by the one or more member addresses associated with the distribution list are able to decrypt the message, by replacing the distribution list address with one or more member addresses that identify one or more members whose public key is accessible by the first server; and sending the message to each of the one or more member addresses that identify one or more members whose public key is accessible by the first server if at least one of the one or more member addresses associated with the distribution list does not identify at least one member whose public key is accessible by the first server.