setting mail-self-blind to t has no effect

[Francis Moreau]

Hello,

I would like to add a "Bcc:" field in my emails that I compose from
emacs (by calling compose-mail).

'mail-self-blind' seems to do the job but setting this variable to
true doesn't work, no Bcc header is added, whereas doing:

(setq mail-default-headers (concat "Bcc: " user-mail-address))

work.

Could anybody know why the first solution doesn't work.

thanks