You will set the portals each property should be uploaded to on each individual property record, but you may also want to check which properties are being sent to which portal.
You can do this for each module via Reports > Properties > Marketing > Portals. Select the relevant portal to see all properties currently being fed to it.
This list of properties will only show those in the current module, i.e. you'll have to run the same report in both the sales and lettings modules to see the various types of properties.