Get rid of load remote content message

To stop being asked if you'd like to load remote content in Mail, open Preferences in the menu bar by clicking Mail > Preferences.... In the Privacy tab, make sure that Block All Remote Content is unchecked. By loading remote content, or by disabling this setting, some senders may be able to tell when you opened a message, and where you were when you opened it.

Change Privacy preferences in Mail on Mac - Apple Support