Have you ensured that your setup will pass email authentication processes?

It has been a long time since email from random hosts is accepted for forwarding or delivery. This Wikipedia may help https://en.wikipedia.org/wiki/Email_authentication

OpenWRT support on GL.inet devices seems to be complex. The following is my understanding of the situation.

GL.inet have an OpenWRT fork on GitHub https://github.com/gl-inet/openwrt This is what is installed on GL.inet devices.

The OpenWRT developers in due course try to work out how to port mainline OpenWRT onto OpenWRT onto GL.inet devices.