Migadu looks very cool! Love that you can setup multiple domains to the same account.
Generally I setup Zoho Mail for all my new projects. It's free up to 5 users but emails like "[email protected]", "[email protected]", etc. can be setup as "groups" that then forward to any of your users, so they don't count towards your 5 user limit.
Since most of my projects start with a max of 2-3 partners, it works great.