Email tracking even on your iPhone

A dear user and contributor of NetworkToolbox just raised a point I would like to share with you.

While discussing my arguments against Web-Mail services and my suggestion to rather use a Mail client instead, he mentioned that he got frightened some time ago even while using his iPhone mail client. What happened was, that he received an Amazon gift voucher from a relative and while he wanted to thank him five minutes later for the gift, the relative told him that he already knew that he received his gift because he’d just received an email from Amazon informing him about it.

So you may wonder how this could have happened even on a relative secure Apple device. The trick is quite simple and widely used by many newsletters, eCards and even regular mails.There are many service providers offering such a feature to companies even garnished with sophisticated statistics about reading time and even the location of the recipient.

What the do is, they just add a small image (visible or not) to each email. This image has an individual name which is different for every recipient. Once the email has been opened, the email client tries to download this image from the server in order to show the email right.

The Server, where the image comes from just responds with the requested image, maybe an empty 1×1 white pixel. So far so good. But any Web-Server, and the server for such an email image is also a Web-Server, will see the requesting IP Address and, of course, the file name of the requested image. Remember, as mentioned before, the file name is basically a unique Identifier which identifies each recipient and the IP Address will help to track down the location and other information such as type of device (e.g. iPhone) as well as the client software the recipient is using. And of course, all of that is being logged and can trigger an email to somebody who is interested in knowing when you read their mail.

But for iOS users, it’s not too bad at all. There is something one can do against it what the dear user found out on his own while googling. There is a setting under Email settings called “load remote images” (or “Bilder vom Websever laden” for the German users) which should be switched off.

It is very unfortunate that this setting is turned on by default but I would strongly recommend turning it off. This setting will prevent the things I mentioned before from happening. The only disadvantage is, that some mails might look a bit strange without images which will no longer be loaded in the future once this setting has been disabled but it’s often not too bad and you can manually force the images to be reloaded. But then, keep in mind, the sender may (and most likely will) track this.

You may wonder why you see images in mails even while “load remote images” has been switched off. The reason is, that in that case, images have been embedded in the mail and thus, don’t need to be downloaded and thus, can also not be used for tracking. The disadvantage for this approach is, that such mails get bigger, are causing more network traffic while sent out and while downloaded on your device.

So, don’t trust the evil.
Stay safe!