@alyssa Not costing money is a hard one. Tuta (née Tutanota) is probably the main one that comes to mind? (Assuming you don't want Outlook.com, or any of the other classic AOL/Yahoo!/similar providers.) Proton offers a small free service (1 GB) but I don't trust its security claims over any other services, probably fine if you don't rely on them. Fastmail is by far the most popular Gmail alternative server I've seen recommended, but it's not free.
@aschmitz isn't tuta that same "secure email" schtick as proton? do you trust their security claims any more?