We use Office365, because we need Office anyway. We initially used a hosting provider email server, but it's not trivial to get the email DNS configuration right, and you risk going in spam. Even after we got our configuration right, we still had occasional "spam" issues.
or Zoho https://www.zoho.com/
There's several previous 'alternatives to gmail' discussions, e.g. https://news.ycombinator.com/item?id=17448108
As someone with many servers and a previous career managing an email service for a university, I would never run my email through anything except G Suite or Office 365. The benefits of those services being "too big to block" is immeasurable.
Do realize that Android only supports GSuite. In other words, by default it doesn't support CalDAV and CardDAV. There are apps for that, but I found those to be a hassle.
Edit: obligatory link tutanota.com