How can I force email programs to show images send in html email using php?

Question

I am sending an html email with php and it includes an image. Some email programs, such as gMail have a \'display images\' button. The user has to click on that in order for

Answer 1

The last place I worked, we were sending out emails that had images in them that would come up automatically, in outlook at least, without me having to explicitly click a show images button.

When I inquired, another developer explained that they simply copied the encoded block of the image from an already sent email into the body of the email. I think this may be a weird sort of workaround they stumbled upon. I don't know if this adds more weight than an attachment, but I could see how an email reader would see an attachment and then ask the user as opposed to read it already in the body and just show it...