Sorry, I did not explain that well at all. Let’s start with your boss, Dick. He send an email TO Tom and CC Harry. He also decides to BCC Jilliane and BCC Mary. The message is formatted to read “FROM Dick, TO Tom, CC Harry”. His email client tells the server to send it to Tom, to Harry, to Jilliane, and to Jane which it does. But the email header says “FROM Dick, TO Tom, CC Harry” with no mention of you or Jane. None of the email clients are told who the email was sent to, only the header info.
When you open the email you see “FROM Dick, TO Tom, CC Harry, BCC Jilliane” because your client adds your email to the header being displayed (but the BCC is not in the real header). When Jane opens the email she sees “FROM Dick, TO Tom, CC Harry, BCC Jane” Her email client knows nothing about you and your client knows nothing about her.
Now when you hit reply-all your email client prepares an email with the header “TO Dick, CC Tom, CC Harry, CC Jilliane”. Possibly you would be listed as BCC in the header, but not likely. When Dick gets the email he realizes you revealed your BCC status. When Tom and Harry get the email they realize for the first time that you were BCC’d in the original. Mary does not get your reply-all since your client knows nothing about her. Tom and Harry likewise don’t know about Mary because they just see the header “TO Dick, CC Tom, CC Harry, CC Jilliane”
Hopefully that’s a better explanation.
oh boy. In the example above, “Mary” and “Jane” are the same person (I started thinking Mary was the other BCC, then made it Jane). What a mess. Sorry about that.