17.3.2. Obsolete Mail Formats
In the original UUCP environment, the prevalent form was path!host!user , for which path described a sequence of hosts the message had to travel through before reaching the destination host . This construct is called the bang path notation, because an exclamation mark is colloquially called a "bang." Today, many UUCP-based networks have adopted RFC-822 and understand domain-based addresses.
Other networks have still different means of addressing. DECnet-based networks, for example, use two colons as an address separator, yielding an address of host::user .[1] The X.400 standard uses an entirely different scheme, describing a recipient by a set of attribute-value pairs, like country and organization.
Lastly, on FidoNet, each user is identified by a code like 2:320/204.9 , consisting of four numbers denoting zone (2 is for Europe), net (320 being Paris and Banlieue), node (the local hub), and point (the individual user's PC). Fidonet addresses can be mapped to RFC-822; the above, for example, would be written as Thomas.Quinot@p9.f204.n320.z2.fidonet.org . Now didn't we say domain names were easy to remember?
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