Yeah, many years ago, where I worked, we had a very basic network using RS232C and I wrote a "messaging system" very like what we now call email. At the time, there was little or no public internet so I can, with clear conscience, say I'd never heard of email before then and so can claim to have independently invented it :-)
Actually, on reflection, it was more like Instant Messaging. Client was a TSR in MS-DOS, server was a PC with 16 serial ports, one for each client, which collected the messages and pushed them out to the relevant person or person.
Biting the hand that feeds IT
