Get the info from exchange server:

 

Connect ISE PowerShell to Exchange server cmdlet

Add-PSSnapin Microsoft.Exchange.Management.PowerShell.E2010

 

 

This command gives you all details

Get-ExchangeServer –Identity <exchange server_name> -Status | FL

 

 

This command gives you the DC which the mail server connects to

Get-ExchangeServer -Identity rd-mail2016 -Status | select StaticDomainControllers, StaticGlobalCatalogs

 

 

Set the Primary DC an GC that exchange will connect to:

Set-ExchangeServer -Identity <exchange server_name> -StaticDomainControllers DC-01.dc.local,DC-02.dc.local 

Set-ExchangeServer -Identity <exchange server_name> -StaticGlobalCatalogs DC-01.dc.local,DC-02.dc.local