Why are long images shrunk in Outlook?

Why is Outlook (2013), shrinking long images. These are basically infographics. Is there a way around this?

Starting with Outlook 2007, Microsoft decided to abandon IE and to use the same HTML engine used in Microsoft Word to display HTML in emails that are viewed in Outlook. This ends up crippling Outlook a good bit, as well as introducing a host of spacing/padding issues that are due to limitations in the way these versions of Outlook render HTML.

The limit you are seeing is the famous 18 inches height limit on images of Word.

You can see this limit demonstrated in the article
Off with its head! Outlook’s maximum height for images in email.

Other resources are :
Large Pictures clipped in Outlook 2007 - Maximum size for images?
Outlook 2013 Still Powered by Word

I don't think there is a real solution to this limitation, except using another mail client than Outlook.

One workaround is to adjust the DPI of images. By tweaking the DPI in Microsoft Word, you can get the image to display a bit taller.

In Microsoft Word goto: Word Options -> Advanced -> General -> Web Options(button) -> Pictures -> Adjust Pixels per inch -> Save and Restart Outlook/Microsoft Word.

The normal DPI value is 96. Bumping it up to 120 will have the effect of displaying more of the image, although not necessary the entire thing. You might also need to use an image editor to increase the DPI of the image itself.