You are talking about email on the public internet. Unless you are encrypting your email body either using s/mime or PGP than there is no such thing as confidential. Even then the envelope with the to and subject are transferred as visible plain text.

That is one of the reasons email from a lot of corporate and government departments contain a lot of mostly unenforceable text about the message being only for he intended recipient.

I understand I can not make it encrypted. (BYW, I do use Identrust for encryption)

Outlook has a "confidential" flag; I was simply looking for such in Thunderbird.

DAVE

dgorelmd said

Outlook has a "confidential" flag; I was simply looking for such in Thunderbird. DAVE

That works only with outlook and exchange.

But I wonder if we could fudge is so Outlook users see it. I will post again after I spend some time searching how outlook does it.

Ok there appears to be an add-on that lets you set the flag outgoing.

https://addons.thunderbird.net/en-US/thunderbird/addon/sensitivity-header/

There is also a bug to implement it that has languished for 12 years. But I see some interesting discussions on how to use inbuilt options with identities and no add-on so I will link it as well. https://addons.thunderbird.net/en-US/thunderbird/addon/sensitivity-header/