[dependenttypes]

Hashes are not a panacea. I see them being suggested as solution for anonymization of ip addresses/domain names/urls/file names/emails all the time but these people that make said suggestions are either clueless or are arguing in bad faith. It is extremely easy to brute-force the majority of said hashes. (in addition to that I doubt that anyone is passing hashed emails as it would make it slightly inconvenient to send emails to said accounts)

[Nextgrid]

It's indeed extremely easy to brute force these hashes when you have a database of the original (plaintext) data stolen from people's contacts which reduces your search space dramatically.

[dependenttypes]

It is extremely easy even if you don't.