I think that last one isn't a modern standard email address -- the domain part is reversed. It's a JANET NRS path (https://en.m.wikipedia.org/wiki/JANET_NRS). The modern equivalent would be [email protected].
The first email address (the ARPA one) is presumably using a machine in UCL as the gateway between internet routing and JANET routing, since the part before the % is the JANET NRS component ordering. The obvious conclusion would be that the mail server he was using didn't have an ARPAnet connection at all.
> ARPA: miw%[email protected] > USENET: mcvax!ukc!man.cs.ux!miw > JANET: [email protected]
miw is clearly Mario Wolczko's username.
Those will be his email address in different formats. The first would route email to him at [email protected] using cs.ucl.ac.uk first as a gateway. The second address format is what's called a bang path, for UUCP email. The final one is a modern IETF standard email address. JANET is a network provider for UK academic institutions, similar to an ISP but structured differently.
You might find these references interesting:
https://en.wikipedia.org/wiki/Email_address http://www.faqs.org/docs/linux_network/x-087-2-mail.address.... http://www.livinginternet.com/e/ew_addr.htm