This is pretty neat idea

Only workaround I know is that you create a rank what user earns when user posts first post. When user earns this rank, platform sends same kind of message to user but via PM or email.

Bad thing here is that this works only when user posts very first post.

I know this solution isnt just what you are looking for but just an idea. 

You could also probably do something with User segments (and custom user roles if needed) and Email campaigns. 

It’s not a pop up, but you could do something similar. 

I’ve been thinking about something like this for awhile around questions, sending them an email when they ask the first question to help manage expectations and promote best practices. 

(Sorry, I just read the topic and accidentally pressed Best answer. I ask mods to remove it. Sorry.)

That's an awesome pop-up banner, @ryanne.perry ! Thanks for sharing this 

I'll share this feedback with our Product team. Who knows? Maybe we'll see something like this in the future!

For a workaround, it is possible to create pop-up banners with scripts, but it requires some heavy dev work.

@ryanne.perry I have set up a popup to appear on our Community. We don’t use it all the time, but when we want to grab the users’ attention. We had a video popping up recently about a rebrand that was coming. We did this with the Third-party Scripts. It is a little fiddly and needs to be tested thoroughly, but it is certainly possible. The only thing I am not sure of is how you could trigger this. But if you keep track of the urls that are actioned (previous and current) you may be able to see when it goes from a post url, like this….

https://yourcommunity.com/topic/new

….to the resultant post page.

However, this is a very high level idea without having been tested (the triggering logic). I certainly believe this is possible though.

I’ve had a quick look at this in our sandbox, you will be able to identify the new post using the inSidedData JSON. If you look at the user.topicsCount record, it will identify when the user has created a new topic. It will also give you the page data and other bits that you could use in the popup.