Sadly, it's not just here. It happens to almost everyone that's not a MAJOR email provider. Email issues about spam (either getting too much of it, or being blocked inadvertently) were the most common source of calls when I worked tech support the past year. The problem is simply that email was designed back when you could (and did) trust literally everyone on the internet to play nice. That, of course, is pretty much the opposite of today's internet, yet we're still using almost exactly the same protocol, just having tacked on things like block lists. Someone's going to have to invent something better pretty soon.