I have been using mutt to send emails from inside another application & it works fine. I have to send html files and currently I have to send them as attachments. So I u
my mutt version is 1.4.x, and I also cannot set content_type=text/html, it is reported as unknown variable.
and I checked the mutt doc, the content_type is only supported by version 1.5.x, such as the latest version 1.5.21.
obviously, html mail was not supported by version 1.4.x.