This is about SNMP, and says nothing about SMTP.
>>> 2021-05-01 simple as in smtp
I suspect the idea is that neither smtp nor snmp are simple when you dig down, despite the name.
And I'd agree with the article, mibs can be maddening
And for snmpv3:
"if you are using SNMPv3 where the authentication and configuration can be amazingly, maddeningly complex for some vendors."
Indeed
% telnet mail.umich.edu 25
MAIL FROM: <william@umich.edu>
RCPT TO: <joe.blow@umich.edu>
DATA
From: William Pietri <william@umich.edu>
To: My Skeptical Friend <joe.blow@umich.edu>
Subject: Who needs a mail client?
You can send email without a mail client!
.
It's harder now, because spammers. But to me it's amazing that something like has been working for nearly 40 years. For perspective, it came out the same year as the Commodore 64.The curious can read the inital RFC: https://tools.ietf.org/html/rfc821