Sendmail originated in the late 70s/early 80s when there were tons of incompatible systems like DECNet and whatnot, instead of just SMTP, and all of them had al

Sendmail originated in the late 70s/early 80s when there were tons of incompatible systems like DECNet and whatnot, instead of just SMTP, and all of them had all sorts of buggy implementations. Today "SMTP" is analogous with "email", but that wasn't always the case. Sendmail won because it could talk to all of them, in bug-compatible ways. Later this feature became more of a liability than anything else and people unfamiliar with the original context are left scratching their heads and going "wtf is this shit?! Maybe those Berkley people really were on LSD?!", but it was a hugely critical feature and without it Sendmail never would have gained the adoption it did – it really was tons better than anything else.