I beleive that at least two of the agencies have no direct email capabilites with the rest of them. Due to classifications in emails, the DIA and the CIA have to use a portal if they want to get with another agency. I amsure there are a few others, but I have no direct knowledge of them.
There are offices where there are air gaps between their internal servers and the internet. Causes issues when software updates are rolled out. ted, put on physical storage devices, then uploaded.
Or so I’ve heard.