The system for preventing unnecessary message duplication in electronic mail forms a message digest of each message received. The message digest is then compared with stored message digests from previous messages to determine if there is a match. If there is a match, this means that the first and second messages are the same, and so the second message is discarded. If, on the other hand, there is no match, then the second message processed because it is assumed that it is a message that is a non-redundant message. The list of stored message digests is culled based on some predetermined criteria to ensure that it does not grow indefinitely.