The reciever might be using Outlook Express. Since this is the receiver's choice on use of what Email client and settings, about all you can do is try a .ZIP attachment with the photo.

From Microsoft:
"To read messages in plain text in Outlook Express:

1. On the Outlook Express Tools menu, click Options.
2. In the Options dialog box, click the Read tab.
3. Select the checkbox to Read all messages in plain text.
4. Click OK.

To read messages in plain text in Outlook:

1. On the Outlook Tools menu, click Options.
2. On the Preferences tab in the Options dialog box, click the E-Mail Options button.
3. In the E-Mail Options dialog box, select the checkbox to Read all standard mail in plain text.
4. Click OK to close the E-Mail Options dialog box, and then click OK to close the Options dialog box."

Bob