I have an Exchange server running emails for a sister company that I created and open relay for in the past and has worked perfectly fine. Until I added a new ISP at the site of the exchange server. All of our host records have been updated. My problem now is that I can receive inter-company emails relayed from the outside server, but I get a failure on sending outside emails form that server.
all other emails handled locally at the exchange server site work perfectly fine.
Any ideas why internal emails will relay but not external just from changing the ISP? Our old ISP is still connected for failover.