The other day whilst virtualising an Exchange 2010 server from Hyper-V to VMware we found that mail routing outbound stopped working.
When looking in the event log we found;
Error ID: 16025
No DNS servers could be retrieved from network adapter %1. Verify that the computer is connected to a network and that the Get-NetworkConnectionInfo cmdlet returns results.
You can see a full Microsoft Explanation here.
Basically when we virtualised the Exchange server, the DNS Settings were linked to Hyper-V VM network adapter, and once this was removed and a VMware Network Adapter was added, the Exchange server was missing this adapter setting.
You can fix this in the GUI, or using PowerCLI, Microsoft details both here.
1. Open the Exchange Management Console. Take one of the following steps:
2a. On a computer that has the Edge Transport server role installed, in the console tree, select Edge Transport. Click the Properties link that is directly under the server name.
2b. On a computer that has the Hub Transport server role installed, in the console tree, expand Server Configuration, and then select Hub Transport. In the result pane, select a server. In the action pane, click the Properties link that is directly under the server name
3. Click the External DNS Lookups tab. By default, external DNS lookups are configured to use network adapter DNS settings. The network adapter that should be used is set to (All available). Take one of the following steps to configure the external DNS lookups.
4.To configure the external DNS lookups to use the DNS configuration of a specific network adapter, select Use network card DNS settings, and then click OK. Select an adapter from the list that appears.