Metadata-free Email: How can SENDER directly, anonymously, and securely ask RECIPIENT’s mail provider to deliver a metadata-free email?

Question

If I want to send emails to friends who use Google, Yahoo, AOL, etc., how can I currently use my local email client to send a metadata-free* email to them?

E.g., is it possible to bypass my own mail provider and directly contact my friend's mail server with an encrypted mail with only one identifying header, TO: [email protected]? Upon decryption, they realize it's FROM: [email protected], sent at TIME, with SUBJECT: subject.

*Metadata-free means the only devices that know SENDER (IP address, username, etc.) contacted RECIPIENT are devices that belong to SENDER or RECIPIENT. An anonymous email account does not pass this test and is thus vulnerable to analysis of its email contacts and traffic.

• Would self-hosted mail servers help in any way?
• Is SMTP the bad guy making this idea impossible?
• Are mail providers the bad guys?

All help appreciated!

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Reviving a forgotten question

Answer 1

Nearly all mail servers in today's world are configured to throw out messages which fail to include that information. The primary reason is simply to prevent spam.

The third best thing you could do is if your friend had their own mail server and you have an account on that server as well. In this case your client would connect directly to their server and the transfer would be within that same machine. However the mail server should also be configured to only allow secure connections (ssl/tls) as well.

The second best is to not use email at all but rather use a chat or voice type program that can establish a direct connection between your two machines using encryption with a pre-shared key that wasn't transmitted in the clear. Of course, traffic monitoring would show that data was transferring between you and your friend even if the contents were hidden.

However, if you are truly paranoid, the best thing is to just talk to them in person by whispering directly in their ear... while in a room that is shielded from all outside means of snooping. Then again you'd need assurances that your "friend" wasn't going to share the contents of the conversation with a third party AND for anyone actually watching your movements they would still be able to know you two met each other.

Answer 2

You can construct an empty From: header by using the special address <>, which is normally used for the source of bounce messages. This may be clobbered by anti-spam.

The more usual solution to this is an Anonymous Remailer. That results in a message "From" the remailer, with a time delay. You need to find a remailer you can trust that isn't blacklisted by the recipient's anti-spam. The "mixmaster" remailers operate in such a way that no single device knows both sender and recipient.

Note that recipient systems may add Date: headers if a message doesn't have one.

Answer 3

I realize this is an old question, but I think it deserves another answer.

The question is unclear on who the adversary is, although the concern with metadata suggests it is either the provider itself, or someone with power to obtain information from them (such as an opponent in a lawsuit or the government, via subpoena or wiretap order).

Note that Yahoo! and AOL are both owned by Verizon Media (formerly named Oath Inc.) since June 2017. Verizon Media, Google, and Microsoft are all U.S. companies.

If the adversary is not the provider, and not someone with legal authority over or illicit access into it, using a webmail account on that same provider may actually result in less metadata stored with the message than any other approach. For example, Yahoo! does not write an IP address, just a Yahoo!-internal hostname, in the first Received: header of e-mail composed using the web interface. In such cases, however, the provider may separately store further metadata.

(Note that the From: header will reveal your Yahoo! username, and you need to confirm with a mobile phone to create a new Yahoo! account, but after Yahoo! dropped or divested a lot of their applications it may be easier to keep the Yahoo! username pseudonymous.)

Also consider the difference between "no metadata" and "no useful metadata". That is, between

(no From: header)

and

From:

and

From: Anonymous <[email protected]>

and

From: d45ff2c85c <fa93347640@invalid>

and

From: "John Smith" <[email protected]>

The first two most literally comply with the requirement "metadata-free", but the last three may effectively provide no useful information to the relevant adversary.