The context: It's a collaboration app, where different people gather to work on the same project. The principle is like the GitHub. So, imagine if GitHub had an inbuilt messenger and you could message only the people that you work on the same project with.
Some people might send spammy messages, so there's a three dot button next to each message(this design is just an example, so no critique, please), and one of the options you'll have once you click on it is to Report Spam.
Which message to show after the user clicks "Report spam"?
A small pop-up appears and says:
1) Message reported successfully
2) Thank for reporting spam
3) other suggestions?