I like Zoho for mail handling, the free tier covers up to 5 user with a custom domain, the small letters is that they don't provide IMAP/POP under the free tier

I like Zoho for mail handling, the free tier covers up to 5 user with a custom domain, the small letters is that they don't provide IMAP/POP under the free tier, but it's pretty easy to set up. If you're concerned about privacy I would evaluate fastmail.com