Any email client may encounter issues with loading images in emails. Issues with images can seriously hamper engagement.
Individual users in Microsoft Outlook can unblock images from the domain "socialchorus.com" or "onfirstup.com", as outlined in this Microsoft article.
However, to assure that images render for your entire team, we recommend working with your internal technology team that handles email security to allowlist images in emails from the following domains. For Outlook specifically, your internal technology team that handles email security can refer to the Microsoft documentation for adding domains to the Safe Senders List in Outlook.
As images may be loaded from a variety of subdomains, and we are in the process of shifting from one parent domain to another, we ask that that you allow both of the parent domains "socialchorus.com" and "onfirstup.com".