Your server cannot do this. However, your Notes client can. I have addressed this in previous ATE questions. Please look through past responses for more information.
Dig Deeper on Domino Resources - Part 7
Related Q&A from Michael Lazar
Learn how to easily keep track of the numbers of incoming and outgoing Lotus Notes email messages to and from your Domino server each day. Continue Reading
Discover what steps you can take if your Lotus Domino server runs out of disk space and you have issues sending and receiving Lotus Notes email ... Continue Reading