You can crop out the horizontal black bars on your video in the Video Library or in the Videos section of your campaign.
In the Video Library, to crop the video, a video has to be in the Saved Folder. Press "Crop" to take away the black bars on your video.
If you don't like how the crop works, you can press the "Uncrop" button to revert your video to the original aspect ratio.
In Videos section of the campaign, you can attach the video to your recipients that you want them to receive. Then, on the bottom left of the video, you can press the "Crop Video" button to remove the black bars.
Please note the "Crop" function is only available for videos with the horizontal black bars. This will not work for videos the vertical black bars.