Re: [Evolution] Bug 738247 - unwanted information disclosure in message headers

[Lindsay Haisley <fmouse fmp com>]

On Wed, 2017-09-27 at 21:41 -0400, d18jf98rw use startmail com wrote:
> No recipient needs to know neither sender's workstation IP address
> nor its real host name.

Normally, headers don't contain the "sender's workstation IP address"
unless the sender's MUA inserts it as a body header, and more often
than not this IP address is an RFC-1918 (unroutable) address which is
useless in identifying the sender.

All headers in an email are technically part of the body of the email
(sent after the "data" command in an SMTP dialog) and I have always
been led to understand that it's not the proper job of a MUA to muck
with these. RFC-2821 specifies that "When an SMTP server receives a
message for delivery or further processing, it MUST insert trace ...
information" (which includes "Received" headers) so information
received by the MUA _should_ contain not the sender's workstation IP,
but the IP of the SMTP server which handled the email for the sender.

a MUA may hide trace information from the recipient to simplify mail
reading, but it absolutely should not remove it, and in the case of
mail stored on a server, received via IMAP, it's doubtful that such
removal is even technically possible.

Trace headers can be spoofed, of course, and as a rule in tracing email
only the Received header inserted by the recipient's mail server can be
fully trusted. Needless to say, spoofed trace headers are NOT RFC-
compliant!

-- 
Lindsay Haisley       | "The only unchanging certainty
FMP Computer Services |    is the certainty of change"
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