Learn your lesson and switch to a custom domain :) that way you will never have to change all your services' email addresses anymore, when you want to switch mail provider.
Yeah, this is gonna be my next move I think. I was using Proton VPN for a while and just recently started migrating my emails there, then they started doing all of this.
I wanted to self host my email anyway, but now I have no excuse. I've been burned by the last team I expected it to come from, I'll be self-reliant now
Most (if not all) domain providers also host DNS for you. After you buy your domain, you'll need to go to the DNS settings and put some records given by your email provider (records are just made of a "type" such as A, MX, CNAME, TXT, a "domain" and the "content").
A .com domain usually costs between 10 and 20 dollars per year. I think it's worth it! There are many domain registrar you can choose from.
I personally like Porkbun, it's cheap and it works great. In the past I used to like the French service Gandi, but it's been recently acquired by a VC and now it's gone to the pooper.