linux-kernel - Re: [PATCH] doc: process: add privacy warning when using some SMTP servers

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Message-ID: <8735brkfrj.fsf@meer.lwn.net>
Date:   Thu, 13 Oct 2022 07:35:44 -0600
From:   Jonathan Corbet <corbet@....net>
To:     sndanailov@...ed4ever.net
Cc:     rdunlap@...radead.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Sotir Danailov <sndanailov@...ed4ever.net>
Subject: Re: [PATCH] doc: process: add privacy warning when using some SMTP
 servers

sndanailov@...ed4ever.net writes:

> From: Sotir Danailov <sndanailov@...ed4ever.net>
>
> Warn the user about "Received" headers and how some
> SMTP servers use them by attaching the user's IP addresses,
> when using some email clients. Add suggestion on how to
> test this behavior and how to avoid it.
>
> Signed-off-by: Sotir Danailov <sndanailov@...ed4ever.net>
> ---
>  Documentation/process/email-clients.rst | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
>
> diff --git a/Documentation/process/email-clients.rst b/Documentation/process/email-clients.rst
> index fc2c46f3f82d..9c49f9b33fdb 100644
> --- a/Documentation/process/email-clients.rst
> +++ b/Documentation/process/email-clients.rst
> @@ -350,3 +350,24 @@ although tab2space problem can be solved with external editor.
>  
>  Another problem is that Gmail will base64-encode any message that has a
>  non-ASCII character. That includes things like European names.
> +
> +Privacy/Security
> +----------------
> +
> +Keep in mind, that even if you're using a working email client, the SMTP
> +server might have configurations you don't like.
> +
> +For example, if you decide to use the Gmail SMTP server with the Thunderbird
> +client, the server will add your private and public IPs into "Received"
> +headers, which are attached to all of your sent emails. This is done
> +to avoid spam and to check where in the routing path an error might have
> +occurred. Gmail's web GUI client doesn't add your IPs, because it's sent from
> +Google's servers directly, not an external machine. Unfortunately the web
> +client is not good for sending patches. You can check if your IPs are present
> +in the headers by reading the raw email source.
> +
> +If you do not wish this behavior, you need to find a provider which doesn't
> +do it or configure and host a SMTP server yourself.
> +
> +If you're concerned, always first send an email to yourself, read the email
> +source and if you see no issues, continue to the mailing lists!

So this seems to be just a description of how email works - the Received
headers always show the path through the net.  Is this really something
that we need to cover in the kernel docs?

Thanks,

jon