LanMail

LanMail operates like an e-mail system for your LAN except that you do not require a mail server to be running to use LanMail, in fact there is only one part, the client section.
Although LanMail does not have a server running waiting for messages that does not mean you can only send when somebody is ready to receive, you can send any time, regardless of what the receiver is doing, even if there pc is turned off.