[Mimedefang] Email resend

Joseph Brennan brennan at columbia.edu
Fri Dec 11 09:49:00 EST 2009

--On Thursday, December 10, 2009 12:42 -0800 - <kd6lvw at yahoo.com> wrote:

> RFC 5321, Appendix B, Headnote 1:
>      "Each recipient address from a TO, CC, or BCC header field SHOULD
>      be copied to a RCPT command (generating multiple message copies
>      if that is required for queuing or delivery).

But this is immediately preceded by

   It is recommended that the UA provide its initial ("submission
   client") MTA with an envelope separate from the message itself.
   However, if the envelope is not supplied, SMTP commands SHOULD be
   generated as follows:

Otherwise, it would be madness to copy all the addresses in header
fields into RCPT fields.

That appendix is about translating non-SMTP submission into SMTP.
If we're discussing non-SMTP data transfer, I can put Bcc: on a web
page and download it, yes :-)

>      the remaining header fields SHOULD be
>      checked to verify that at least one TO, CC, or BCC header field
>      remains.  If none do, then a BCC header field with no additional
>      information SHOULD be inserted as specified in [RFC 5322]."

This is an error in the RFC.

I remember this point because many years ago there was an MTA popular
in England that rejected mail with a format error if it had none of
to, cc, or bcc.  We didn't generate mail like that, but once in a
while we forwarded something that hit the rule.

RFC 822 required either Date, From, Bcc, or Date, From, To.  Not in
the main text, but in appendix A.3.1.

RFC 2822 changed this.  I once argued this with a postmaster in
England.  Section 3.6 says:

   The only required header fields are the origination date field and
   the originator address field(s).  All other header fields are
   syntactically optional.

RFC 5322 repeats the same wording in its section 3.6.

Joseph Brennan
Columbia University Information Technology

(going for the pedant award, David)

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