The first Nigerian Prince scams started over email.

Mayhaps. But Spanish prisoner letters were known much before that. Which is basically the same advance fee scam but with a different cover story.

Here is a story which describes one such letter from 1913: https://web.archive.org/web/20020815055745/http://www.samizd...

Snail mail scams like that were common for decades prior. My mates dad nearly fell for one once.