I use GNUs for most of my email needs, but also have notmuch for rapid search of my inbox. Trouble is, when I choose a message in that notmuch search, it doesn’t open it with gnus but with its own message-mode spinoff called Message[Notmuch]. In GNUS I have an automatically added BCC address (my “sent-mail” inbox, which is downloaded across devices to sync what I’ve sent). How can I get the same automatic BCC added to anything I send in reply with Message[Notmuch]? I found a solution:

Answer

I found a working answer by using customize-variable message-default-mail-headers and adding: “Bcc: address@place.com "

It looks like this in the end (in my emacs-custom.el):

'(message-default-mail-headers "Bcc: address@place.com"
")

Note that it is required for each mail header line to end in a newline.