Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
The first thing that comes to mind from what you have asked about and what you have mentioned is, that you might have a slightly weak internet connection.
An attached file or image - especially when large or high-detail/high-density - may be slow to load, if your internet service happens to be not the fastest.
Do you know how to view or monitor the internet or network data throughput speed of your computer's network connection? if so, I advise looking at it while viewing an email with attachments, and see if this is the true explanation.
OK. Is this problem on the same computer each time despite the different locations and connections?
Or is it the same Outlook account, but on different computers (locations, connections) ?