Re: 2822upd-06 Sender

Frank Ellermann wrote:
> Hi, on the DKIM list a poster claimed that Sender is OPTIONAL.
> Looking for the evidence why that's wrong in 2822upd I found
> an unclear SHOULD:
> 
> 1:  from multiple authors    => MUST (table 3.6 and in 3.6.2)
> 2:  one author = transmitter => SHOULD NOT (redundant, 3.6.2)
> 3:  otherwise SHOULD (3.6.2)
> 
> I don't get case (3), why is it only a SHOULD ?  For anything
> that's not covered by (2: one author = transmitter) I'd expect
> a MUST:
> 
> - Otherwise, both fields SHOULD appear.
> + Otherwise, both fields MUST appear.
> 
> What could be a plausible excuse to ignore the SHOULD in (3) ?

Nothing wrong with the statement in 2822 section 3.6.2:

    If the originator of the message can be indicated
    by a single mailbox and the author and transmitter are identical, the
    "Sender:" field SHOULD NOT be used.  Otherwise, both fields SHOULD
    appear.

-1 only trying to change something that isn't broken and on enforcing 
something that will immediately make existing systems non-compliant for 
no reality plausible reason.

-- 
HLS