Automatic attachment preview in Mail

I've used a post in a previous discussion to run a command in Terminal to turn off automatic attachment preview and leave it as an icon. It worked perfectly. However, it doesn't seem to have changed in on other people's email programmes. Mainly, each time I send an attachment (often a photo) it appears as an icon to me, but still as an image in their email (outlook) thus they are unable to download it effectively. Is there something else I ought to have done to reflect in their email what it is like in mine.

This was what I used in Terminal:

defaults write com.apple.mail DisableInlineAttachmentViewing -bool yes

Thanks