By default, Evolution blocks all images from the internet. You can enable the loading of images in messages from just your contacts or from all senders by following these steps:
1. Go to the menu, click Edit and select Preferences.
2. The Evolution Preferences window will appear. From the left pane, select Mail Preferences.
3. Select the HTML Mail tab.
4. Under Loading Images select either Load images in mail from contacts or Always load images from the internet.
5. Click Close.