You have Nginx configured. The access logs never pick up any POST message content. You get 405 error messages. What do you do?
This will send a message payload -- but not via POST. It may not work for your situation. To get a message to be sent to a website (a listening web service), craft a URL that does not necessarily exist, but retain the domain name or IP address.
Run a command like this: curl http://x.x.x.x/SPECIALTESTTOAPPEAR
(But replace x.x.x.x with the domain name or the IP address of the website; replace the "SPECIALTESTTOAPPEAR" with the string of your choice.)
Go to the access.log file on the back-end of the Nginx server (e.g., run sudo find / -name access.log). You should see "SPECIALTESTTOAPPEAR" in the logs.