When I attach files using M-x mml-attach-file,
C-x m does attachments as expected but
M-x mail just sends the text
<#part type="text/plain" filename="~/Downloads/coding_style.c" disposition=attachment description="modified coding_style.c"> <#/part>
Why are these different when sending mail works with both?
I know nothing about mail in Emacs, but running C-h k C-x m tells me that C-x m runs the command compose-mail, which is different from mail. This is presumably why they behave differently. You can find out more with C-h f compose-mail and C-h f mail.
C-x m calls compose-mail but not mail. According to documentation compose-mail:
Start composing a mail message to send. This uses the user's chosen mail composition package as selected with the variable `mail-user-agent'.
for mail-user-agent:
Your preference for a mail composition package.
but mail from sendmail.el:
Edit a message to be sent.
So, if set, compose-mail could call mail from sendmail.el for creating and sending email.
