As far as I know, that emoji question due to the same reason IDN is allowed in URLs, and they even went as far as their own RFC for it https://datatracker.ietf.

As far as I know, that emoji question due to the same reason IDN is allowed in URLs, and they even went as far as their own RFC for it https://datatracker.ietf.org/doc/html/rfc6530 https://datatracker.ietf.org/doc/html/rfc6530 (very similar to the 6532 cited repeatedly, but more important(?) because every system in between the sender and recipient needs to know about hops, whereas the recipient is the terminal node's problem The LHS is, as far as I know, because the LHS of _all_ email addresses is "if it's deliverable", modulo the rest of the call-outs from the rest of the quiz