Network Working Group (and many others) deprecate x-sender specifically
because:
Many mail clients on personal computers are now using a non-
standard "X-Sender" header to identify the originator of a message
without the implication that the sender has a known deliverable
mailbox (unlike the "Sender" header). Usually this "X-Sender"
header is constructed from the credentials used to login to a POP
[POP3], IMAP [IMAP4], or NNTP [NNTP] server. Such credentials
often do not refer to a deliverable mailbox, and therefore MUST NOT
be used to construct a return or reply address.
I disagree strongly with your contention that all headers are equally
untrustable. *Untrustworthy* they may be, and always in need of better
authentication (a whole new protocol built around RFC 1113 encapsulation,
perhaps?), but there is an implicit trust placed in the standard headers
that you can't possibly deny. To say that the To: header "[has] no value"
is a bit silly for a vendor of an SMTP relay. And my statement about "x-"
is completely correct: it "signifies" an untrustworthy header BECAUSE the
"x-" headers are unstandardized, hence not to be processed by RFC-compliant
relays, whereas the standard headers, despite your objection, are to be
taken as relatively trustworthy and used to deliver mail. X-sender: seems
to me to be a comment on the essential untrustworthiness of Sender:, but
that doesn't change the fact that whatever ends up in the Sender: position
is trusted (in the absence of a From:, right?).
Regards,
Sandy
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]On Behalf Of Len Conrad
> Sent: Wednesday, October 25, 2000 3:05 PM
> To: [EMAIL PROTECTED]
> Subject: RE: [IMail Forum] HEADER QUESTION
>
>
>
> >Thing is, the "x-" in x-sender signifies an untrustworthy
> header, so you're
> >sort of working against yourself...
>
> x means experimental, if, not an Internet standard.
>
> All headers are untrustable, and so have no value as identification
> or authentification.
>
> Len
>
>
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