Arnt Gulbrandsen wrote:
> 2821 4.5.5 lists some types for which you should use the null
> path. It doesn't forbid using <> for types not on its list.
> 3461 5.2.2 (d), 3834 3.3 and 5230 5.1 add to the list, and I
> would not be surprised if other RFCs add more and code does
> even more.
2821bis explicitly mentions RFCs 3461 and 3798 in this section.
RFC 5230 is an application of RFC 3834. There is no reference
in 2821bis. I recall that John discussed it with Keith, maybe
that should be fixed, adding an RFC 3834 reference in 4.5.5 (?)
4.5.5 says that MAIL FROM: SHOULD be not empty in scenarios not
covered by standards-track RFCs mandating an empty reverse-path.
^^^^^^^^^^^^^^^^^^^^
IMHO exploring the far end of SHOULD on the border to MUST.
Frank
