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This question relates to an answer on Skeptics.SE. Read the comment where somebody wrote "Even if you forward someone the email you received, we can't be sure you didn't fake it." Is this statement true?


Let's say that Stack Exchange sent me an email and I have no reason to doubt the email is fake and not from Stack Exchange. I want to show my friend that I received an email from Stack Exchange, but cannot physically show him/her the email. If I forward the email to my friend, will he/she be able to independently verify that the email is indeed from Stack Exchange?

Equivalently, is the statement "If you forward someone the email you received, we can't be sure you didn't fake it." a true statement?

I know that there are questions on spoofed emails. This one is specifically asking about forwarded emails and checking whether or not they are spoofed.


My interest in this is not purely hypothetical (although the described situation is). If you are really interested, read the comments here.

  • This question is not about email spoofing, and is not about security concepts. This question is a pure email question. – schroeder Jul 17 at 7:27
  • @schroeder Sorry, didn't know! Can I do anything to improve this question? – Barry Harrison Jul 17 at 21:19
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For almost all mails one can not check if this is the original mail which was forwarded.

This can only be mostly done if the mail was cryptographically signed by using PGP or S/MIME and if this signature can be validated by the recipient. Even then this is not a full prove since the signature usually only includes the content of the mail and not the mail header.

One might also attempt to verify a DKIM signature contained in the forwarded mail. But, this is only proof that the mail was transported by a specific mail server and not that it was send by a specific user. Also it is not unlikely that the mail get invisible changed when forwarding it and thus the DKIM signature will no longer match.

  • Do we have a stack that could handle email protocol questions? I do not think this is a security question. – schroeder Jul 17 at 7:28
  • Thanks for answering! Do you mean it's hard/impossible to verify a forwarded email? – Barry Harrison Jul 17 at 21:21
  • @BarryHarrison: That's what I've tried to say clearly with the first sentence. To cite: "For almost all mails one can not check if this is the original mail which was forwarded.". – Steffen Ullrich Jul 18 at 3:44
  • @SteffenUllrich Sorry, didn't pay enough attention there. – Barry Harrison Jul 19 at 6:07

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