It's kinda hard to help someone with almost no details provided. Are you referring to Outlook.com using a browser? Or are you referring to the Outlook desktop software? If so, which version? Or are you referring to Outlook (hotmail) on your Windows Phone?
Is there any notification like "links and images have been blocked" or so? This typically happens for items in the junk folder, but can aso apply to any other folder, if you played around with the settings.