I never used this address anywhere so comparatively not much. Oddly, almost none of it is in the spam folder. The other interesting bit is that someone seems to have been using this address for online purchases and lease agreements (fraudulently, most likely).
I have a very old Gmail account. For purposes of this discussion, call it sergey@gmail.com. I often get real email sent to addresses like sergey2000@gmail.com. By "real" I mean important stuff that people would miss if they didn't receive it. In the beginning, I used to follow up. I'd occasionally get a reply from the sender asking a question like "OK, thanks, could you send it to her for me?" I concluded that some people have a "horseshoes and hand grenades" attitude toward email addresses -- close but not exact is good enough. Maybe they can't remember all the digits in the address, so they put what they can remember and hit send.
Similar situation, but I've had people think I'm "hacking" them when I respond.
As a result, within the last 15 years I have only contacted someone back once. That was about funeral dates/coordination.