The bangs in the address were essentially how the old email systems routed messages (UUCP, IIRC.) There was no "cbmvax.com" it was just "cbmvax".
You'll find traces of the old routing scheme all over Usenet messages from the period. I believe the system still runs today, though not within circles I travel. This is relegated to the oldest of wizards and warlocks -- an age unknown which exists only in legend.
