I received an email with a coupon offer and viewed it within webmail (should not matter which provider).

I wanted to print my offer, but my printer was down, so I forwarded the email to a friend so he could print it for me.

My friend opened the forwarded email within his webmail. Within the email is an image that states 'click here for the offer'. Right-clicking on that image and selecting 'Copy link' within the browser results in the link to the offer being copied to the clipboard.

All is as expected... except that the link to the offer contains his email address! When I view the original email, the link contains my email address, as expected.

How is this possible?

How can an email address change itself just by being forwarded?

How can a forwarded email know the recipient's email address?

UPDATE: Thank you for the responses thus far. We repeated the steps above, this time first clearing all cookies (including flash cookies) and web history on both systems. The link in the forwarded email still knows the email address to which it has been forwarded. Interestingly, it actually enables the offer for that email address as well, assigning what looks like a new UUID as part of the offer link.

UPDATE 2: Looking at the email headers, there is an In-Reply-To and a References header item that each include an email address for the original sender. The Content-Type is multi-part/alternative; boundary="[string]". The actual content is almost certainly HTML.

  • If the offer is from a website you have both used in the past and entered your details into, then it's possible that they just stored cookies on your PC that contain the info, however I assume this isn't the case. If you feel comfortable to forward me the email, I could tell you exactly how they did it :) – MyNameWouldGoHere Aug 28 '15 at 8:00
  • @MyNameWouldGoHere Thank you. How do I forward it to you? I have also updated the question above with additional information. Specifically, they are not using cookies to accomplish this. – RockPaperLz- Mask it or Casket Aug 28 '15 at 21:04
  • Were you able to test it in a non-web email client (Thunderbird, Outlook...)? Can you confirm the kind of content type that the e-mail is composed of (HTML, plain...)? – nKn Aug 28 '15 at 21:13
  • @nKn I have not been able to test it in a non-web email client yet. I will update the question in a moment with an answer to your other question. – RockPaperLz- Mask it or Casket Aug 28 '15 at 21:24
  • @RockPaperLizard hit the forward button (just like you did to your friend) and send to my email address: postmaster@chloecrayola.co.uk and I will get back to you – MyNameWouldGoHere Aug 28 '15 at 21:28

Interesting. The only thing that comes to my mind is that the DATA section of the e-mail contains some script that is capable of getting the e-mail address that logged in within the Webmail client, perhaps knowing that this webmail client stores its data inside a cookie named X and fetching the data from it and therefore appending it to the link.

I wonder why they would want to do that, though.

Possible tests you might want to perform:

  • If your webmail client is capable of opening the plain e-mail content (something like the the source code), you could see exactly that's happening in the DATA section.
  • Try forbidding cookies for the Webmail site, clear cookies, log out, log in and see what happens with the link.
  • If your webmail client doesn't provide a source code option, try opening the e-mail in a client like Thunderbird which provides this capability, which is by the way another interesting test to try to see how it behaves with dedicated clients.

Ugh. This is both embarrassing and frustrating. Many thanks to "MyNameWouldGoHere" and "nKn".

Well, let me own up to what was my own mistake (well, more of my friend's mistake, but I'll own it), and how bad UI/UX design contributed to that error.

From what I believe I have now determined, both my friend and I received this same email offer, with different embedded offer codes inside. When I forwarded him my email to print it for me, his webmail client grouped both emails together into the same "conversation" (even though one email was from me to him, and the other was from a third-party to him).

Within his webmail client, there are not sufficient or appropriate cues to indicate that the webmail client had combined two emails into one "conversation". What looked like one email was, in fact, two different collapsed emails. He had no idea he also received the same offer.

I discovered this by having him perform a search within his webmail using the title of the email. It turned up two separate emails. Yet when he views his inbox, only one of those is shown. From there, I deduced what had happened. I had him send me a screenshot of his webmail, and I can certainly see how the bad UI/UX design led to his mistake, which led to mine.

I'm almost certain this is what happened. I apologize for the error, and thank everyone for their help.

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