Originally, this parameter is introduced to control proxying mode for
non-CERN HTTP type proxy (including gopher proxy) by rewriting a URL
(or pointer) with gateway-_-URL
or proto://gwHost:Port/-_-URL notation,
where the gwHost:Port part is generated and embedded by DeleGate.
This parameter is introduced to customize the representation of the gwHost:Port part. It is a representation of the entrance port of this DeleGate which must be resolvable and reachable from clients. To make it be most usable, the default value of gwHost is that of current network interface of the host of this DeleGate through which the current client reached to this DeleGate, and it is represented in raw IP address number so that clients can reach the DeleGate even if they don't know how to resolve the host name of the DeleGate.
Exceptionally, if the entrance port is specified with with an explicit network interface like "-Phost:port, the default value of DELEGATE is set to the host:port.
By specifying an optional ProtoList, you can limit to which protocols this proxying is applied. URLs (or pointers) in a response message are rewritten prefixed with "proto://gwHost:Port/-_-" so that the request to it is directed again to this DeleGate (at gwHost:Port), if the protocol is included in the ProtoList.
Thus you can disable the proxying mode specifying non existing entrance port and an empty ProtoList like DELEGATE="-:0:-all". But this can be done more simply by RELAY parameter and it is disabled by default in recent versions.