I am currently testing moving isp, i have made the required mx and reverse dns changes and everything checks out. I tried switching over and incoming mail is working fine but we are not sending. I quiclky changed back to the old isp and everything is fine. I noticed in my exchange 2010 server we are using as a send connector (on the organisational configuration/hub transport tabs) the old isp as a mail relay. I'm not familiar with this and have inherited this setup, should i simply disable the external relay to allow outgoing mail to flow?
Any help would be appreciated