curl: (6) Could not resolve host: application

It's treating the string application as your URL.
This means your shell isn't parsing the command correctly.
My guess is that you copied the string from somewhere, and that when you pasted it, you got some characters that looked like regular quotes, but weren't.
Try retyping the command; you'll only get valid characters from your keyboard. I bet you'll get a much different result from what looks like the same query. As this is probably a shell problem and not a 'curl' problem (you didn't build cURL yourself from source, did you?), it might be good to mention whether you're on Linux/Windows/etc.

I replaced all the single quotes ['] to double quotes ["] and then it worked perfectly. Thanks for the input by @LogicalKip.

Example for Slack.... (use your own web address you generate there)...

curl -X POST -H "Content-type:application/json" --data "{\"text\":\"A New Program Has Just Been Posted!!!\"}" https://hooks.slack.com/services/T7M0PFD42/BAA6NK48Y/123123123123123

In my case, putting space after colon was wrong.

# Not work
curl -H Content-Type: application/json ~
# OK
curl -H Content-Type:application/json ~