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.
You are correct, it was just UUCP routing, very common on the internet up to the late 80s. SMTP and NNTP running on top of TCP/IP took over quite early on, so most of us never had to deal with UUCP.
More than you ever want to know:
http://en.wikipedia.org/wiki/UUCP
