UUCP and Usenet aren't, but blocking port 25 is a violation of net neutrality principles. Albeit a widely accepted one now since at this point you should have an option to use a more secure port to send emails such as 443 or 587 (outlook's SMTP over SSL). That isn't to say that port 25 can't be secured to use TLS and other solid security measures, but it normally isn't.
what is this Net Neutrality principles you speak of? I've never seen anywhere that says an ISP can not block Port 25. In fact most block incoming on port 80 as well.
Maybe the Company should change their outgoing mail server to something else?