Thank you for the compliment @shelldozer. 😊
Feel free to ask questions. I’m happy to help.
I believe in enabling others to learn from my pain.
I think what you’re wanting to do is imminently possible to do. It’s also what I’m doing.
I used to run my MTA on a Linode VPS for the reasons you mention.
Earlier this year I changed things a bit where the MTA now runs in a VM in my house and uses a VPN to the same Linode. (For simplicity, you could think port forwarding through the VPN, but it’s more than just that.)
If this is new to you, I can HIGHLY recommend @mwl’s Run Your Own Mail Server book as a great 0 to 60 starter. If you follow his directions you will end up with a functioning mail server that should meat your desires / requirements.
I’m happy to discuss further / answer questions if you want.