By default, Outlook 2016 for Mac doesn't automatically download pictures or photos in email messages if the images are stored on the Internet. This practice helps to protect your privacy because downloading an Internet picture can alert the sender that your email address is active and that you received the message. However, you can turn off this preference or choose to download Internet pictures only from your saved contacts.
Note: This procedure doesn't affect attached pictures or pictures that are embedded in the body of a message.
On the Outlook menu, click Preferences.
Under Email, click Reading.
Under Security, select the option to specify when you want to automatically download pictures from the Internet: either in all messages, or only in messages from your contacts.