Is there a way to exclude certain sites and subdomains from Google Alerts?
At the moment there are a couple of sites and a couple of subdoamins of other sites that are throwing up false positives (dev sites, our own blog running on subdomain.mydomain.com etc).
So try creating a Google Alert with
-site:subdomain.mydomain.com (add multiple instances of that for each site you want to exclude). According to a discussion on the Google product forums, that worked a few years ago.
You can also see from that discussion that a feature to allow using
site:subdomain.mydomain.com (without the leading minus sign) to only send alerts from a specific web site has sometimes worked and sometimes been removed by Google. So there's a possibility that
-site:subdomain.mydomain.com no longer works in Google Alerts.