Yahoo mail will not accept a sketchup attachment
Right-click on an object and the context menu pops up. The context menu is different for each kind of object, which is why it’s called a context menu: the picks listed on the menu offer actions that make sense with the object you right-clicked on.
What is the significance of that?
Zip up the SKP file into a Zip archive and try that.
Be aware the Yahoo Mail may have a file attachment size limit. Gmail does.