Some email clients (Gmail) or operating systems use EXIF data to decide how to display an image.  This data is stored in the properties of an image. If it was originally taken upside down, the image orientation is retained and will be transmitted to the end user unless deleted.  The image in the WYSIWIG and all previews will look correctly, but depending on the email client, it may not save its intended format unless the data EXIF data is removed.

You can remove EXIF data from a photo in Windows by:
  1. Right click the image and select Properties.
  2. Select the Details tab.
  3. Towards the bottom of the menu select "Remove Properties and Personal Information".
  4. This will allow you to choose what data you would like to remove, and if you want to keep a copy of the original.