Delivery reports and read receipts in PHP mail

Question

Does anyone of you know off by hand what mail headers to add in order to get a read receipt and delivery report? This now being when you use the normal PHP mail function. No

Answer 1

Gmail blocks methods such as:

img src="http://yourdomain/tracking.php?id=EMAIL_ID" width="0" height="0"

This is because the image is retrieved from a proxy. Since the URL contains variables and not a real image file, the image will not be shown. The tracker would be useless.

I've personally experienced this as I build my own newsletter system.