A number of my personal sites end up blocked by corporate firewalls. It’s slightly infuriating. Even my own company. I got in a literal fight with IT needing to justify the why in why I needed access to my own website. Like I can live without it, but it’s nothing but my blog where I rant about tech. The why should be why is it blocked to begin with. The default state should not be blocked .
Default approach of a firewall. When it doubt, block it. But IT has really outdone itself and grew to something that could be the largest threat to an open internet. The same could happen to mail, where you can only use "certified provider" or you will just be filtered out. Spam and phishing are a problem, sure, but recent IT strategies are highly questionable in this regard.
I think it of as a result of high profile hacks. Either a company is hacked once and they go way overboard trying to ensure it doesn't happen again. Or, some high profile company gets hacked, some C*O's see it, overreact and decide they're not going to be next.