It seems as if the jenkins proxy settings (Plugin Manager > Advanced) get ignored by the confluence publisher plugin.

AxisFault
faultCode:

{http://schemas.xmlsoap.org/soap/envelope/}

Server.userException
faultSubcode:
faultString: java.net.ConnectException: Connection timed out
faultActor:
faultNode:
faultDetail:

{http://xml.apache.org/axis/}

stackTrace:java.net.ConnectException: Connection timed out
...