ok we currently have an exchange 2010 env. and are adding new AD sites in another country. we need to deploy Exchange 2016 in those new AD sites. I understand they will be in the same org which is great, but we have a firewall between the two sites. What ports do I have to have open between the sites so that the exchange servers will communicate and route mail.
obviously port 25 for mail flow but what else?
Thanks in advance!