@kytta I also have the same inner debate always. Currently I use my main domain for both web activity and email. I dont think it is a bad idea. Regarding having linkage to internet persona, I use my name in most places, so that doesnt really affect me.
But if you are giving this a fresh start, note that people might think of your new domain as spam too. If it doesnt relate to you, and has an arbitrary webmail landing page, feels kinda spam/phishing.