Previously (2 years ago), someone on a list I'm on reported they tried Zoho (after using Google and before switching to Fastmail) but A) found customer support to be terrible and B) their email was being treated as spam by a couple of big providers (Yahoo and AOL). I'm not too concerned about the customer support opinion but delivery is job #1, it's a major reason why I won't consider self-hosting email.
B/c I use gmail for my personal email, I found that if I didn't have a unified inbox, I would miss reading important emails.
Just a heads up: I was looking through their website [1] recently, and found that they'll let you go onto the trial if you're solely looking to move away from their email service.
[1] https://www.zoho.com/mail/zohomail-pricing.html#:~:text=Can%...
I also, back up any important emails. The rest, I can lose and not cry.
Edit: Purelymail might be interesting if they had calendar syncing. Maybe when they've grown a bit more.
Zoho has done so, with the removal of POP/IMAP for their free tier without any notice.