Are you using Outlook (or similar) for mail?
It sounds as if, previously, attachments were configured so that they were viewable as embedded or inserted images and that he changed the preference on how attachments are viewed.
I don't use Outlook but I'm sure that someone will be along shortly to help and explain how to re-set the configuration or preference.
__________________
".... This world wasn't built for people in wheelchairs ...."
.