[_jcrossley]

I think so. Another recent entry is purelymail, which I love because it's a flat rate for unlimited domains. I'm trying to spin up multiple "small bets", and per-user pricing is unreasonable, and for better or worse, I don't want a single catch-all email.

A secondary benefit for me is that Purelymail is cheap ($10/yr). But a major downside is that the CalDAV implementation doesn't yet support Accepted/Rejected scheduling responses. It's fantastic that they have CalDAV at all, but this one feature would seal the deal for me.

I don't mention it to suggest you could directly compete on that unlimited-users value prop, but it's an example along the lines that max_ suggests.

One that comes to mind is integration with recent ActivityPub / fediverse stuff. There might be cool design space there