Some people are obnoxious assholes and keep doing reply-to all on a chainmail that is going through the system. It sucks, and somehow people keep replying to "not answer this email!".. Wankers.
So, I went to exchange to put these users (whom I don't know and never have any contact with, nor will I in the future) on my blacklist. Lo and behold... That wasn't possible, because:
"The e-mail address for the sender (******* removed for privacy ******) is internal to your organization and cannot be added to the Blocked Senders list. E-mail from senders in your organization will never be treated as junk e-mail."
Yup, you can't decide for yourself, bollocks!