Lotus Notes sometimes adds unwanted spacing to tables in EDMs or HTML emails.
Try nesting all the tables inside a wrapping table and set the wrapping table BG Color to match.
eg. In my case Ive set the wrapper BG colour to white, so that the blue space you see is filled with white.
NOTE: These Spaces may also be cause by <br> tags or <p> tags at the bottom of the table cell, above where the unwanted space is occuring… I noticed this as cells with images only, dont cause this unwanted space below their cell. I havent tested this though.