It seems to me that since the original 128K and 512K can run BBS software to share e-mail and files via those old networks, and later, services like FidoNet allowed those dial-up networks direct access to the internet, there must be a way to send and receive e-mail via the internet on a 64K ROM Mac.

Shouldn't there be a way to run a localized version of a FidoNet-type software to convert a serial null-modem connection to an IP-based one? The goal would be to allow a Mac 128K to send an receive e-mail over the internet, using nothing more than a serial connection to a modern OS X Mac (via the handy-dandy Keysapn USB serial adapter).