iMessages are being delivered to the recipient over WiFi. Text messages are not being delivered to the recipient over WiFi. Both messages are being delivered over cellular, when WiFi is turned off. When cellular option is turned off, iMessage works, SMS text does not. I don't see how it could be a cellular issue. Maybe I wasn't clear in my original post.
We believe it might be a port being blocked in our firewall. Working with our network security office now. Thank you everyone.