When we send broadcasts or autoresponders we have the choice of sending the email messages as text, HTML, or MIME. When we send is a text email, it's strictly just plain unformatted text. There are no colors, no different font sizes, no images, just plain text.
HTML emails can include images, hyperlinks to webpages, different font sizes, bold, italics, different colors, etc.
When you write an email to a friend, it's typically a text email. When you receive an email from a big company such as Amazon.com, it will be an HTML email. Since there are images and different colors, it is HTML.
MIME is simply sending the email as both text and HTML and letting the email application decide which version to display to the recipient. In the early days of the Internet and checking emails on non-smart phones, MIME allowed the sender to feel more confident that the end-user will be able to view the email. On the non-smart phones, it would show the simple text version of the email. If they check that same email on a computer, they would see the full HTML version.
Nowadays, there are very little devices that require text-only emails so sending as MIME isn't as necessary anymore.
Choosing which style to send as is easy! When creating a new message within an autoresponder, you'll be presented with two tabs, "text" and "HTML". The "text" tab will be selected by default. You'll notice if you click the HTML tab, you'll see all the editor commands appear that allow you to customize the look and feel.
If you do want to send your email message as MIME simply enter your content on both the text tab and HTML tab.