If nothing else you could do
system("nslookup www.google.com", intern=TRUE)
In response to your edit:
domains = c('www.google.com','www.badtestdomainnotvalid.com','www.yahoo.com')
sapply(domains, function(x) system(paste("nslookup", x), intern=TRUE))
This will return a list of vectors, you can manipulate as you see fit beyond that