is the from: an to: gmail address the same? I ask because Gmail hides the received email and pretends it is the original you send. They also remove anything in the BCC fields and replace it with "undisclosed recipients" resulting on a lot of complaints over the years on this forum about the BCC entries disappearing from the send email.

This is the first time I have ever seen someone says they see BCC names even in the sent folder.

So, Matt, do I understand you correctly, it's Gmail that sends the original back to the sender? I made the test using a couple of other email accounts that I have, and the Bcc: recipients did NOT show up in either the message or the header as received through those accounts in Thunderbird. But the one I got on the same Gmail account I sent it out on did indeed look very much like the original, in that the Bcc: recipients were there in the message and in the header. So the secret of who-all got the 'blind' message is safe, despite one's own message received appearing to tattle. Thanks for the explanation.

Oh, and yes, the Bcc: recipients are in the original outgoing message that's in the Thunderbird Sent folder. I would expect this to be the case, although I never paid attention before.