And if we can BYOD, will they let us have a catch-all? I want to be able to sign up for a service with company@mydomain, so if I get spammed I know who sold my data / got hacked and didn't admit it. I think Google Workspace and Proton are the only major email providers that support that. But the former means switching to a business account which doesn't always play nice with Google's other services, and the latter doesn't work well with other email clients (by design, of course, but I'd be worried about lock-in as a result).
Regardless, I have reservations about trusting Mozilla with webmail. The "Looking Glass" fiasco from years back showed they don't mind selling out to brands, and their current financial trouble might make them more likely to do so again. I realize the Firefox fans will downvote me for saying that, but it's a legitimate concern.