Comment by pseudohadamard

It's not so much that SMTP won, it's that X.400 lost because it suuuuucked. Anyone who's ever had to work with that piece of s*t, as opposed to rhapsodising over what it could theoretically do, can tell you stories about this. It made Microsoft Mail and Lotus Notes look good in comparison. Notes actually did X.400, so imagine Notes but even suckier.