Email could have been X.400 times better
Summary
An historical comparison of X.400 and SMTP, detailing how X.400 promised richer, interoperable messaging but proved too complex for widespread adoption. The piece argues SMTP's simplicity and incremental standardization enabled internet email to prevail, while outlining the niche roles X.400 still plays in aviation and government. It also touches on how email security features evolved later with standards like SPF, DKIM, and DMARC.