Hmm, I don't do any intro if I remotely know the person. My emails look like this:

Subject: General topic + call to action

Brief introduction to problem, ideally one sentence. A call to action, like getting some info or whatever.

Extra details if needed, which is pretty rare. Two to three sentences max.

Thanks,
my name
relevant other info like title

No intro, that's available in the email header. Just don't put in filler...