If there are no specifications for a certain product, you can display an alternative text (or html) where the specifications are normally displayed within the product block. For example "specifications not available".
The (optional) alternative value is only shown in the e-mail if there is no product specification for the product. Once there is one, then only that one specification is shown.
It is possible to set up an alternative value in the product block template. Contact your Spotler partner if you want to add an alternative to your product specifications.