Oh well, back to the drawing board. I found a lot of reasons for various issues but managed to handle them all. Except one.

As this Macro scales all images (which at first seems a great idea) I just noticed one that doesn't need to be scaled back and should definitely NOT be: The logo in my signature. As I am a 'newbie' with VBA in Outlook I am not sure if there is code that would exempt items in the signature.

Even though the signature is a hosted image on a website it still gets the '50% treatment' that I was so glad to have in the body of the email. If you happen to have a solution for this one, please share.

Other than that, i found that if the image is pasted into an email with pasted objects set to "square" rather than the default "in line with text" this can also cause the VBA to simply do nothing. No errors. No stops. Nothing happens at all. I almost didn't catch this one as this is a setting i have set to 'square' on one system only and as this is a hard to find setting in the first place i had almost forgotten where it is controlled.

When i remembered how to change it back to the default 'in-line with text' things started working normally for the VBA.