Hi hogscape,
Thanks for using Apple Support Communities. We see that content doesn't load for some emails in Mail on your MacBook Pro. We're happy to help.
If you haven't already, make sure that your Mac has the latest software.
Update macOS on Mac
If the issue persists, close the Mail app and test the issue again.
Quit apps on Mac
Let us know the results. Does this issue occur when connected to a different Wi-Fi network? Does the issue occur with multiple email accounts? Please include additional error messages and any other troubleshooting steps that you may have tried.
Have a great day!