x.x.x.x:XXXX:1433.
This doesn't make any sense. IP cannot have a port associated with it. IP will get you till the machine; and port number will take you to the app which listens to that port.
It has to be either XXXX or 1433. Not both!
Edit
What you should do is, talk to your network admin folks to configure port forwarding on your NAT - this means that the NAT will listen on a port you specify, and all communication which reaches this port will be forwarded to the MS SQL Servers internal IP + another port you specify, for example: 148.25.6.22:1433 => 172.16.0.61:1433. Now, if your appserver connects to 148.25.6.22:1433, the packets will reach the MS SQL Server at port 1433.
A similar question: https://stackoverflow.com/a/31619341/6785908