This. So many people don't take the 10 minutes to configure DMARC, DKIM and SPF. I've been hosting my own domains since 1996 and I haven't ever had a problem with any of them sending mail to any of the big hosters. If your DMARC passes and you actually have a policy set to REJECT you're almost guaranteed to not have a problem as long as your domain isn't a few days old. The first thing I do for any new domain I plan to use is get all of those items configured ASAP and start sending mail into Google and O365 to test and thereby end up in their domain analysis.

Given all the horror stories I've moved all but one domain off of Gmail (mainly to preserve my grandfathered G-Suite. I don't use `@ gmail dot com` for anything other than Google services. And if you are using GMail back it up! MailArchiva [0] is free for less than 10 mailboxes and works well. In this regard at least you still have access to your mail and can possibly prove something if those emails contain any identifying information (hopefully not, but you never know what will help).

If your email is that important to you then don't run it for free. Pay for someone to host it - I've been more than happy with Fastmail for many years and also use paid for ProtonMail accounts with custom domains.

At the end of the day if you don't control the domain and don't pay for the service I don't feel like I can trust the provider to do the right thing or expect any level of support. Bring email back from the monopolized "free" tier!

[0] https://mailarchiva.com/