I’m using Dns.GetHostEntry() to resolve an IP from a DNS name. When I update the dns (Route53 in this case), it gets updated in a few minutes and I can resolve to the new ip basically every other way except in Unity. Unity keeps the resolved ip somehow cached. Most likely a feature of Mono and ServicePointManager.DnsRefreshTimeout seems to be not implemented so that cannot be used to set the cache lifetime.
Have you been able to solve your problem? We’re facing the same around here.