Ask HN: In my messaging side-project will emails or handles work for people?

I'm considering that maybe people want the ease of simply logging in with their email, and the simplicity of entering (perhaps autocompleted from contacts) their friends email to set up a messaging connection with them. I'm also considering that, maybe emails and spam are already so overloaded, people may value "a fifth channel" they can use out-of-band to chat with whom they choose. Say I can share my handle with a subset of people who may or may not intersect with those who have my email. Or I can publish my handle, while keeping my email secret. If anyone cares to share some thoughts or experiences, that works. The Q's not asking for a prediction of the future, just a reflection or a tale from the past.