On iPhone 6/7/8/SE, we are seeing a vertical white line down the side of the email, splitting all images and content into portions of approximately 90% and 10% (the 10% being to the right of the white line). I'm stumped. We're using tables and the usual VML tricks for background images (there's only one background image in use, in one of the table cells). Any ideas? Elements/attributes for me to look for?