In general, you only want to spend your time with emails where genuine interest is reflected. They may talk about themselves and what they offer, but do they talk about you and what you offer. I'll give a little example of both:
GENERIC EMAIL (Don't waste your time responding):
Hi there,
I am a Twitch streamer with 10,000 subscribers. Can you send me a Steam key so I can try your game?
GENUINE EMAIL
Hi interestick,
I saw your game on Steam and I really like the concept of a survival card game. I think your game would be a good fit for my Twitch channel where I play similar games. I have 5,000 subscribers. Can you send me a Steam key so I can try your game?
The key takeaway here is this: If someone is genuinely interested in something about your game (playing it, promoting it, etc), then they will be usually be specific about it.
It's very easy in today's world for people and companies to get massive lists of email addresses and just write and send generic form letters to see who takes the bait.
Just recently, a company asked me if I would be interested in their Instagram marketing service. It sounded good at first, but I noticed a few red flags:
-- They never mentioned my name or my game specifically
-- When I went to the website, they had "Instagram testimonials" -- but when I actually went to Instagram, only 1 of those 7 accounts actually existed.
-- All of the testimonials on their website had strangely similar Instagram naming conventions: Usually a word with a number, like snowflak3 or catl0ver
Needless to say, I didn't bother responding to them.
And it sounds like you might already be doing this, but I would also recommend setting up a Google alert for the name you use to publish your games and the names of the games themselves.
Hope these tips help!