On Thu, Nov 27, 2025 at 02:36:30PM +0100, Sébastien Hinderer wrote:
Is there a way to add a "Content-Language" header to outgoing e-mails? As I understand it, the question is not completely trivial because such headers should be added for each MIME attachment and not in the message's main headers.
I don't see anything built in. However, editing a message with headers[1] lets you type the header and its value(s) yourself, and puts that header in the message -- for the simple case, a message with just one body part (text/plain), where all headers are in the main header section.
Mutt can compose a message as multipart/alternative: text/plain and text/HTML. (You compose Markdown -- plain text -- and then Mutt generates the HTML version.) I doubt you can get Content-Language: into both alternatives in that case.
[1] $edit_headers=yes, or 'E' in compose menu
