Exchange management shell commands. These were tested on Exchange 2010 and may vary for newer versions. Also make sure that the server selected for the Global Catalog (GC) is actually a GC. The DC and GC settings can also be modified via regedit, but of course be very careful when using regedit.

List Exchange settings

get-exchangeserver -identity EXCHANGESERVER | fl

Set static DC or GC

set-exchangeserver -identity EXCHANGESERVER -staticdomaincontrollers DC1.COMPANY.COM
set-exchangeserver -identity EXCHANGESERVER -staticglobalcatalogs DC1.COMPANY.COM

Check and attach mailboxes

clean-mailboxdatabase -identity "MAILBOX DATABASE NAME"