Thank you both for the replies.
I accept that the sender might be at fault but it has never happened before and it is not just one sender with whom I have the problem but every email with an attachment that I receive with a scanned document or a photograph. Word documents and video attachments all open as normal.
From what I have read I too think that the attachments are being shown in the Preview pane but no amount of double clicking will open the original "attachment".
A similar thing happens when I send attachments, be they photos or scanned items. When I open the email after sending (for what ever reason) the photo/scanned item is already open in the Preview pane but I cannot open the attachment by clicking on it.
I don't know if any of this makes sense but as you might have guessed I am clueless where computers are concerned both with their technology and terminology.
Thanks for trying.