K.P. Cijsouw said:
If the BCC field never leaves the senders machine, then how is it possible
that the receiving mailserver knows to which mailbox/user the mail has to be
delivered?! I'm 100% positive that this tool exists (at least for Outlook
2000).
The *fields* shown in the UI for your e-mail client have nothing to do
with e-mail delivery. They are there for YOUR convenience. When you
have your e-mail client send a message, it compiles an aggregate list of
all recipients specified in the To, Cc, and Bcc *fields* displayed in
its UI. Using this list of recipients, your e-mail client then issues a
RCPT-TO command to the mail server for each recipient. Once that is
done, your e-mail client issues one (just one) DATA command that
contains your message (headers, blank delimiter line, and body). The
mail server hasn't a clue which recipient was specified in which field
and it doesn't care. It has been told who are the recipients by the
list of RCPT-TO commands that it received. The recipients never get to
see the original list of RCPT-TO commands that the sender issued to
their sending mail server.
The headers in the message (what gets sent during the DATA command) is
whatever the e-mail client puts there. E-mail clients are NOT supposed
to included the Bcc field in their header section in the message but
some did (back when dinosaurs roamed the Earth). The e-mail client
should only insert To and Cc headers that match on the values specified
in the To and Cc fields in the e-mail client's UI. Since the Bcc field
was never copied to a Bcc header in the message, there is nothing within
the message's headers to indicate who were the Bcc'ed recipients. And
since recipients never get to see the list of RCPT-TO commands issued by
the sender to their mail server, there is no way for the recipient to
know who got Bcc'ed.
Even for old e-mail clients that used to include the Bcc header in the
message based on the value of the Bcc field in their UI (as, say, an
option to do so), many receiving mail hosts will strip out that header.
It wasn't supposed to get transmitted so it gets stripped out if
present. The whole point of the Bcc field is NOT to create a header
with that list of recipients. It is, after all, a BLIND carbon copy.
If the sender's e-mail client was misconfigured to include a Bcc header,
and if the recipient's mail host doesn't strip it out, then no
additional software is required to see that header. Just view the
headers in your e-mail client to see them. If the Bcc header is there
then you can see its list of recipients.
