We are migrating our Umbraco websites to new 2019 Web servers for multiple environments including PROD. The Website is up and running but Courier is not able to connect to new remote hosts. If I change back to my old host in courier.config, it works. new ones don't. is there any other settings needs to be done?

Below is the error:

Exception occurred System.Net.WebException: Unable to connect to the remote server ---> System.Net.Sockets.SocketException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond