It shuts most of them down effectively, but also keeps the door open in case they really would have an opportunity that would work for me. And over the course of a decade or two working in the same town, it built a network that I can call up when I do want work, letting me drive the process on my next search.
2) Cold emails which obviously were sent to thousands with a canned message or a pitch completely foreign to your competence. Don't reply to those, you'll only get more of them and your connection to those recruiters won't have much future value either.
I get probably a dozen emails in bin 2, for every email in bin 1. Most of the bin 2 emails right now are from a company called "Data Revolution" which seems based in the UK and that I can only assume is either completely automated recruiter spam (Their profile pictures seem oddly stock-photoish), or some sort of dystopian gig-economy recruitment firm for people who rather send emails than drive Ubers.
The bin 1 contacts have actually returned on several occasions with those really rare job profiles I describe in my response, so this does work very well. I basically have a dozen people looking at job ads for me so I don't miss those one-in-a-thousand jobs I'm looking for.
I find it counter-productive to foster bad relationships with recruiters, although many of them have treated me most barbarously (I'm over 40, which means that I'm "radioactive").
LinkedIn sells a fairly pernicious type of spam, which allows recruiters to craft messages that seem to be quite personal. I have made the mistake of responding to these, in the past, as if they were personal. No harm in that, but I really waste my time, and the recruiters'.
But the worst kind are the recruiters based in India - they keep sending irrelevant emails for jobs in the US where I don't even live, and no matter how many times I flag them as spam in Gmail they keep going through. I think they found a loophole to go around Gmail spam filter, so the only way is to manually add them to a filter.
Just out of curiosity, especially in UK there seem to be companies that scrape CVs from job web sites, feed all the addresses into databases, and send these indiscriminate emails if a few keywords match. And if one responds, they ask for a telephone call and might call dozens of times.
At some point, I was actually wondering whether it would be possible to automatically get phone numbers of that kind of people into said CV data bases (with an obviously useless auto-generated CV that however has matching keywords).