Because of one smartass customer who insisted on doing exact RFC 822 validation, I implemented exactly that. And yes,

zKcknV|NGv.lI66vR#@X`QcRK4K.R`?NpA.Gc2Kqzue9.%&nb1kGWp/./#Och$RQv

is one of the test cases for a valid addr-spec. See (or generate) some others at https://github.com/mormegil-cz/rfcemailvalidator