I moved a handful of my domains MX records to Fastmail so that family members had a super simple UI and good UX experience. It isn't free but in some regards n

I moved a handful of my domains MX records to Fastmail so that family members had a super simple UI and good UX experience. It isn't free but in some regards neither is Gmail. Either way it is very affordable. The one concern I have seen mentioned is that their headquarters is in AU and they have some very dystopian government policies but I have no idea if that has ever impacted anyone. Fastmail handle DKIM signing of your emails. I've not had any delivery issues with them as of yet after several years. If using your own domains it is easy to set up a canary alias for each vendor to limit cross-marketing and cross-market tracking. They also allow creating aliases on several of their domains but finding the alias you want may be harder.