i merely quoted the tutorial for entering caches elsewhere on site, certainly that list is valid caches.. it's the list winmx itself uses, but not all caches suit robomx as well as some others (the main mxstuff indexing cache for example is almost useless for third party clients) ...
the ones i gave above have been picked out as being suitable types
try adding
chatpcs.winmxconex.net as tig suggested is likely to be suitable (or wouldn't have been cited)
and
cache.taboochat.net
as well
you actually don't need a huge list of 30 hostnames as those ones all resolve to the same 4 or 5 caches anyhow & robo will connect the first time it gets a response it can use