Messenger behind reverse proxy? Ports to open in Firewall?

Maybe I didn't read the right documentation pages ☹️
My questions

  • Is it right, that the client communication is running via port 8300? And this has to be open to the world?
  • With this in mind it doesn't seam possible to run the Messenger behind a reverse proxy, like can be done with GMS or GW WebAccess?
  • Thus Messenger should be placed in the DMZ and not the internal network?