Free email is fine. Just make sure to own your own domain and MX records. Worst case you switch to somewhere else and keep on mailing.
My rational is to align my interests with the company running the infrastructure for a fundamental component of my digital life.
Free email is fine most of the time. Until it's not. I want to limit my "until it's not" exposure.
https://www.arin.net/resources/fees/fee_schedule/#ipv4-ipv6-...