This is true. gmail has been proxying all user content via it thus showing Mountain View,CA as its REMOTE_ADDR. This is true only for gmail clients. The same logic has not been working on Gmail via outlook or any other mail client.
Most email tracking companies rely on these details to differentiate the recepients of the mail.
I dont think there is a work around. But if there is one we would find out soon given that these companies have a lot to lose.
Meanwhile, you could try using HTTP_X_FORWARDED_FOR or disposition notification headers. But given that this can be messed with, there isnt much option left but just go back to making people click on links!!!
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…