Comment by grandinj

Yeah, as someone who had to implement a protocol stack to talk to a X.400 server, it was not fun at all. Weird encodings, monster spec, all sorts of weird server-specific stuff that you had to do exactly right if you wanted the server to accept your email.

Compared to that, when I implemented RFC821/822 (i.e. SMTP) mail, the hardest part was the weird line-encodings, but other than that, the spec was ___so___ nicely readable and pragmatic.