Welp I guess this is the perfect example of companies not deleting your credentials and account info when asking for it... I deleted my Notion account several years ago. And completely randomly today got an email from them about data retention, assuming this is one of those "important" emails they have to send out. Sadly, years ago I wasnt using email-aliases like I am today, so still stuck with them having my email. Fuck I hate this so much. Thought I'd just share this lesson, use alises my friends!
With self hosted email and at least Proton Mail (and probably other paid solutions), you can set up a "catch all" address. With that, any non existing email gets redirected to one; for me, I have spam@domain.com so, while myname@domain.com goes to my inbox, thisaddressisinvalid@domain.com and, I don't know, walmart@domain.com both go to spam@domain.com. I don't need an individual entry for every alias and I can specifically block any address that's particularly spammy or compromised.
I hear that you can have a similar setup with something called SimpleLogin, but I've never tried that.