Robert A. Rosenberg wrote:
I seem to remember that it ALSO needed the absence of a Cc header
to trigger this injected listing.
Plausible, maybe RFC 2076 just didn't mention this detail. RFC 2821
7.2 doesn't discuss any details, and RFC 3552 22.214.171.124 is only a copy
of RFC 2821 7.2.
Somebody on the EAI list got me to dig out a stoneage bat book, with
that at hand I find:
| If the header of a mail message lacks all recipient information
| (lacks all of the To:, Cc:, Bcc: header lines), sendmail adds an
| Apparently-To: header line and puts the recipient's address in
| from the envelope into the field of that line. This behaviour
| is hardcoded into sendmail.
| The Apparently-To header name is not defined in RFC822. It is
| added by sendmail because RFC822 requires at least one To: or Cc:
| header, and neither is present.
Trying to fix missing header fields by adding a different header
field was a rather odd idea... :-) And "apparently" it did not an
Apparently-To when there was (only) a Bcc, but it stripped the Bcc,
again arriving at no RFC822 recipient at all. Oh well... And I'll
fix my header field name review request, thanks for your hint.