I also used Zoho for mail, it was pretty nice and they had quite robust support once I got an issue. I left them only because I already pay for iCloud+ and come

I also used Zoho for mail, it was pretty nice and they had quite robust support once I got an issue. I left them only because I already pay for iCloud+ and comes with custom domain support, so I realized I didn't need to pay for another service. The Web UI of the mail and the mobile app was also quite good.