.csnet is a hostname suffix that was used for identifying nodes in the Computer Science Network (CSNET) not directly connected to the Internet but reachable through special gateway systems. It was never installed as a top-level domain in the Domain Name System, but parsed in the message routing logic of mail transport agents (MTA).
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bitnet
.bitnet was a pseudo-domain-style suffix used in the late 1980s when identifying a hostname not connected directly to the Internet but possibly reachable through inter-network gateways. In this case, it indicated that the hostname preceding it was reachable via the BITNET network. This was one of...