Rather good actually. It needed a nice front end for modern user types (no idea there is a command line, let alone what a command is). MTAs such as sendmail and MMDF allow message delivery to a programme, such as uudecode (in badly configured installations, a source of a security problem), so that the recipient got his "multimedia" message.
I note that the article author seems to think MIME and WWW simplified email addressing. I can only say that, in 1986, I was working with sendmail, UNIX mailX, MH, etc. using "firstname.lastname@example.org", developing UNIX-VMS gateway protocols and an address book. The predecessor was the "!" separated path style. But even that was being remapped by sendmail to the "@" style in cleverer implementations. UKsendmail hid most of the nastiness, for example.
I find it interesting, as an aside, that Steve Jobs was so prescient and quick to spot the possibilities. While I appreciate the reservations of the academic, Jobs's willingness to take a risk and break new ground was usually well founded, as demonstrated by even the current Apple products and their galvanising effect on the industry. It is a shame that the academics did not seize the chance. Perhaps one needs a strong self-belief to do this It is ironic that, now, only OS X can still compile what must have been more or less pure UNIX code. One could call that, "open".
X.400, by the way, was far better and more functional than its terrified detractors claimed. I used it, as did many firms needing security and reliable delivery. PP and Quipu were rather good and used, for instance, for early pager and SMS to X.400 email gateways. ISODE is, I think, still going.
X.500, leading to LDAP, came out of this set of standards.
So do n't be too sniffy about things that happened during your childhood or adolescence.