+X - Extension Query Reply
+Syntax: <id> X <servername> <routing> :<reply>
+Example: -1 X channels.undernet.org 5/127.0.0.1/6667 :OK kev Logged in
+States: N/A
+Next State: -
+Comments: Used to deliver the reply to an extension query to the iauth
+ instance. The <servername> parameter indicates the origin of the
+ reply. The <routing> parameter is the same as was used in the X
+ message from the iauth instance, and can be used to pair the reply
+ with the original request. The <reply> parameter contains the text
+ of the reply.
+Compatibility: This is an Undernet extension and ircd does not send
+ it.
+
+x - Extension Query Server Not Linked
+Syntax: <id> x <servername> <routing> :Server not online
+Example: -1 x channels.undernet.org 5/127.0.0.1/6667 :Server not online
+States: N/A
+Next State: -
+Comments: Used to indicate to the iauth instance that the server
+ specified in the X message is not presently linked to the network.
+ This will not detect the extension query being lost due to a network
+ break, so iauth instances should further implement a timeout
+ mechanism for extension queries.
+Compatibility: This is an Undernet extension and ircd does not send
+ it.
+