automatically, unless you tell it to do otherwise. This is to prevent your computer from downloading harmful or offensive images. When the recipient of a blocked image responds to your message his/her computer downloads the image when the message is sent - that's why you see it in the response.
To rectify matters, tell your contact to do this:-
1. Go to the Tools menu and select 'Options'
2. Click the Security tab.
3. Clear the 'Block images and other external content in HTML e-mail' check box.
Don't forget to advise your contact that by doing this he/she will see every image that is sent - whoever the sender is.