The blind that fits the given description is a social network / app where you can register with a company email but are otherwise anonymous, so that you can post anonymously with people from your company.
A lot of people (at least where I work) are disgruntled there. I get the feeling they joined because they were unhappy and want to vent about the company anonymously, but with people who know what they're talking about. Maybe I'm just projecting though.
There are possible implementations where it could be done, e.g. they don't store your email address after registry or they only store the hash - which I hope they've done. There are also possible mitigations from the user's side, e.g. when registering send the verification email to an alias that is a list of people so that you are not uniquely identified by it.
