Cannot send email from exchange server 2016

I'm setting up a new domain with windows server 2012 R2 and exchange 2016.  To test the mail server I had it sitting outside of my firewall with a public IP.  Everything was working correctly until I moved the server behind the firewall.  Now when I try to send email using OWA both internal and external says "you don't have permission to perform this action" and the mail is left in drafts.

The only changes were a physical cable move from my ISP router to my internal switch and changing the IP on the server from a public IP to a private IP.

The network is  cable modem -> router/fw -> switch -> server.

The router/fw is limiting my ability to test the server internally alongside the current email server because it doesn't allow me to port map more than one external IP.

I've read a bunch of articles online and made some of the changes but none of that has helped and I don't think it should apply here.

I did change internal DNS to point everything to the internal IP.

I would assume that I should at least be able to send email within the server.

Any help is greatly appreciated.