I suspect most here experience the same thing. On a daily basis you'll receive numerous emails or adverts from a variety of channels.
My question is simple: What makes a good one? Or what makes a bad one?
The vast majority are simply copy/paste templates where your name is replaced. The sender clearly doesn't know you. Instead I'm looking for data if targeted adverts would be better. For example, an advert quoting your recent OSS contributions, StackOverflow questions and blog posts that in turn links back to the job description. This is in contrast to the mass blanket approach traditionally taken.
I don't believe standard recruitment companies could perform this research step but my belief is that such adverts would increase engagement, even if nothing comes from the lead directly.