I have a server build as follows built for a small school with limited hardware:
1x Server 2012 running on physical server. Roles: AD, DNS, DHCP, WSUS, File Server.
1x VMWare server hosting an Exchange Server and a small Linux Box.
Both physical servers have adequate RAM and CPU and are new HP servers.
I have a problem with the exchange server. When the exchange server was built, there was an issue with the internet to the school so we proceeded without fully patching the server over the internet. After the internet link was fixed, we found that outbound mail was delayed but did deliver BUT inbound email was not bouncing with the error:
#554 5.4.4 SMTPSEND.DNS.NonExistentDomain; nonexistent domain ##
The KB article said this was an issue that Exchange 2013 Cumulative Update 6 could fix, however, sadly, after the CU6 update, all mailflow has stopped. I have checked with the configurations exchange server and everything is in place with accepted domains, email policy, DNS resolutions, Mail Routing using DNS and not Relay Server etc.. Late yesterday afternoon, I proceeded to point the exchange server to the google DNS servers to resolve Domain Names, after which a large number of exchange services failed. After a reboot, I was not able to log into the exchange server and authenticate to the AD. I am quite sure this is a bug, as I have built many exchange 2007 and 2010 exchange servers before and this is the first time I have come into this problem. Exchange is licensed (Standard) and so is the operating system (Server 2012 R2 Std).
Hope there is someone who can shed some light into this.