The last tine I tried to switch from Gmail it was a complete failure and the main reason was spam. I get --a lot of it-- and I've even had trolls sign me up for spam lists before. I think conceivably the biggest reason to use Gmail is now gone because LLMs could classify spam almost perfectly.

If I were to try switch again I'd look for a mail service that specifically mentioned using LLMs for spam. If they say they're using one of the "open source" spam prevention solutions I can almost guarantee you its not going to do shit. They aren't good enough to catch all the permutations of serious spammers (who probably test on those tools before sending anyway.)

Edit: it also occurs to me that you could simply download all your mail locally and pipe it through a local model. That could actually work really well, tbh. If you hosted that on a server you would have the advantages of online access with gmail-grade spam filtering at any standard host.