Multi Part MIME Emails

Can anyone confirm if this is default functionality in suite?

When sending an email from an email template (without “Send Text Only” cheked), the html version is used to create the text version (basically by stripping out all the tags). So, that is to say, you cannot send one email with different content for the html and text version. It’s one or the other.

Is this correct?

If so, do you know how to send one email with the both the html version content and the text version content in it? In my experience this has always been standard in various email software’s.