I am saving attachments from Outlook to a Sharepoint Document List. There is no problem with that.
Buuut depending on the name of the file, the file has to move to a subsite or another. To do this, first I have to check if the subsite exists, if it does the file moves there and if it doesn't It sends an Email.
I'm stuck checking if the subsite exists, and I feel like it should be easy.
I was able to find a solution for this as I ran into the same issue today.
The overview is check for the /Shared Documents/ folder info on the site. If it does you return true, if it doesn't or the get metadata fails you return false. Doesn't do exactly what you asked but is usable for my work around. In my case it is being used as part of a larger application so I return the data to powerapps.
Hope that helps!
You can set the variable to any site name you want to pass, I just used a static one for testing.