To “take control of your email” I recommend buying your own domain, but not self-hosting.
Having your own domain will allow you to migrate from one email provider to the other, as you stop being locked in to them with their domain.
If you do not want to use Google or Microsoft, I recommend mailbox.org (used this one for a long time, but had to change, because I wanted to send emails from my aliases). Tutanota is also good choice.
Protonmail is also there as one of the more popular alternatives to Microsoft and Google, but I find them too expensive.
Why am I not recommending self-hosting email on self-hosting reddit? Unlike other services, which you can host at your home (which simplifies a lot of stuff and allow you to avoid subscription), you pretty much need VPS for selfhosting email. If your needs are simple, both mailbox.org and tutanota will cover your email needs for 3 euro per month. You don’t have to think about security, spam, email delivery, building trust with other email providers. It’s their responsibility, not yours. Good luck doing it cheaper on VPS.
I personally use M365 business basic, it’s very reliable but exchange online might not be user friendly. However price to value ratio is just unbeatable.
Why do you want to migrate from pfsense? I know there is big push from reddit communities to opnsense, but it’s mostly for ideological, not technical reasons. The actual product is really solid with less updates (but the security ones like openssl are done quicker on pfsense), PFsense business version is cheaper both for hardware and software version and most importantly it works for you right now, without wasting time. I’ve been using opnsense for many years in my homelab and also had to work with pfsense in business environment (not that much though) and from security and cost perspective I do not see reason to use opnsense. It’s either less stable or more expensive than competitor.So why bother with change?
As for clearOS, I wouldn’t waste time on it. I think after HPE bought them, they mostly stagnated. Looking at their github, nothing is really done:https://github.com/orgs/clearos/repositories
same with their blog.