When an image does not load in Outlook it will be replaced by a red "X" icon in the phishing simulation email. The main reason for this is because Microsoft Outlook is preventing the image from downloading automatically or your office network is blocking the connection to Phish Insight to retrieve the image.

To resolve the issue, please perform the following steps:

• Check if you have completed all the steps to Add Phish Insight to your Exchange / Office 365 Allow List.
• Add the Phish Insight email sender ‘pawt@mailrelaysrv.com’ to your Safe Senders List. This will allow images to load automatically. The instructions vary based on your mail client, but here is an article about deploying a safe senders list via Group Policy for Outlook:
  https://support.microsoft.com/en-us/kb/2252421
  
• Images from real phishing emails are normally blocked by Microsoft Outlook. You may also consider keeping the images in the phishing simulation blocked to mimic a real attack.