Proton has a great free tier that may work well for you. I’ve used them for a while now and it’s been great. They have what is probably the most feature-complete private email service out there (unless I’m forgetting something). The main nitpick I have with them is how little they focus on Linux, but that applies more for their other services than email.
For the most part it really is. A lot of what it does I would do anyway, but it has that by default, which saves a lot of time for me every time I install it (which is quite often due to my endless distro-hopping). Not everything works perfectly, and a lot of that is intentional (such as spoofing the timezone). I would definitely recommend giving it a shot, and if something doesn’t work well you can probably just turn it off (and they’ll probably explain how in their FAQ).