I understand that you are currently seeing some error messages related to the image. Is this an outlook account? Usually, this error message is related to the external environment.
The first thing to check would be to see if you can try reproducing the issue when sending it to an entirely different personal email address to see if you can reproduce. The other thing it could be is an issue outlook has with your domain, and not with the email images.
There are a few ways to test this:
Insert an image from a URL so it's not using our file hosting and doesn't use their domain in the email, check if this renders out.