Hello Bruno,
In your second screenshot for Fax and E-mail setting, I see the e-mail address which is maintained as default sender maintained again in "Send all e-mails to the the address" option.
So no matter which e-mail address you maintain in your blast, it will be sent to the e-mail maintained in this checked option which again is same as the default sender. Try changing this, check and confirm.
Regards,
Chandan