Engineers get badly mis-targeted emails from recruiters all the time. Sometimes dozens everyday and many of them are way off the mark for all kinds of reasons (often hilariously so, but I'll save that for another post). Seriously, it is not out of the ordinary for an experienced software engineer to get 20 emails from recrutiers every single day!
A good way to get replies is to play with this idea and try subject lines that make fun of the fact that many recruiters are blasting out badly targeted messages.
I bounced these off some friends (who are software engineers) and I think some of these are a little corny but basically they would stand out and get replies.
Here are some debates you can try to start with more experienced developers (who may have strong opinions on this stuff, so watch out). I think most people will take the bait and reply, but this is probably going to be a little bit less effective than the section above.
Did you know most software jobs these days are in an open-office environment? Open offices suck. Most engineers hate them. They are noisy, they make it hard to concentrate, you don't get much space and every time somebody catches a cold everyone ends up getting it. Check out this thread on Hacker News if you don’t believe me. https://news.ycombinator.com/item?id=19482159
Do you have a remote req you are filling? I can think of a ton of great subject lines to throw at people. By the way, these will only work on people not already working remote!
By the way, I have worked remote for the last year and a half and I'm not sure I'd ever go back to an office unless I was doing a job that was more business or management oriented. So in my opinion you are going to get bad response rates about on-site positions if you are talking to somebody currently working remote.