Released: March 2021 Exchange Server Security Updates

I tried to install this patch on an Exchange 2016 server running on Windows Server 2016 and it failed catastrophically. I first updated to the latest CU, restarted the server, and tested to confirm everything was working. Then I tried to manually run the KB5000871 installer. It kept giving errors about processes related to Windows services that needed to be killed. I killed them and clicked "Retry" to continue the update but the update would start over and then come up with the same error because the services were being triggered to start by something in the OS. I disabled the services so they couldn't run and installed the update. After that, the Exchange server was hosed. Luckily, it's a VM and I had taken a checkpoint right before installing KB5000871. I tried removing KB5000871, restarting, and having Windows update check for updates but it didn't find KB5000871 as an available update. Now I've got a client who is scared to death that their server is going to be compromised and I have to tell them I can't get the update installed because it seems that no matter what you do, it won't install properly if you try to manually run the patch.