Re: Mandatory From field, anonymity, and hacks

On Sat January 29 2005 04:23, Hector Santos wrote:

> The first question.
> 
> Which software is responsible to make sure the format is correct?  The MUA?
> The SMTP Receiver?

If that's a general question, the answer is a combination of
MUA and MSA (RFC 2476).
 
> Most, if not all SMTP receivers detect valid headers and add what is
> necessary.

No, MTAs are not supposed to alter the message content except
to add trace fields (Received, Return-Path).  MSAs are permitted
to make specific modifications.
 
> Based on RFC 822 (A.3.1.  Minimum required), a valid RFC 822 header is one
> that has:
> 
>     Valid RFC header = Date: && From: && (cc: || bcc: || To:)
> 
> This was relaxed in RFC 2822 , where a valid RFC 2822 header is one that
> has:
> 
>     Valid RFC header = Date: && (From: || Sender: || Reply-To:)

RFC 2822 does not require a Sender field unless there are multiple
authors, and does not require Reply-To under any conditions.

> Are you proposing further relaxation as follows?
> 
> 822:    Valid RFC header = Date && (cc || bcc || To)
> 2822:   Valid RFC header = Date && (Sender || Reply-To)

See above and RFC 2822 section 3.6.

Yes, your error in interpretation of those RFC aside, the intention
is to make the From field optional. [MIME media type message/rfc822
has yet another set of rules, but a From field is not mandatory
there; however if a From field is absent, there must be at least
one of Subject or Date fields.]
 
> From a point of view of Completeness:
> 
> Technically, a message needs no headers at all.

No, a message must have a message header, and that message
header must have at least one header field.  See RFC 822
section 4.1, RFC 2822 sections 3.5 & 3.6, and RFC 2046
section 5.2.1.

> So the next and final question is:
> 
> Is a RFC header required in the DATA stage at all?

If that's an SMTP question, yes, because SMTP transfers
messages, and the message format (822/2822) requires a
header with certain fields.