Mautic doesn't support sending plain-text email yet, but you can still mimic plain-text kinda email, here is an example:
I'll show you two ways to use this....
Method 1: Code Mode
Go-to mautic code mode, and use the following code:
<!doctype html>
<html xmlns="http://www.w3.org/1999/xhtml" xmlnsv="urn:schemas-microsoft-com:vml" xmlnso="urn:schemas-microsoft-com:office:office">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta name="viewport" content="width=device-width" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>{subject}</title>
<style>
img {max-width: 100%; height: auto;}
</style>
</head>
<body>
<div data-slot-container="1">
<div data-slot="text">
<p>Hi, Name</p>
</div>
</div>
<div data-slot-container="1">
<div data-slot="text">
<p>Put ya body message here..</p>
<p>You can also add a link the normal way:
<a href="#">a link</a>
</p>
</div>
</div>
<div data-slot-container="1">
<div data-slot="text">
<a href="{webview_url}" style="-webkit-text-size-adjust:none;-ms-text-size-adjust:none;mso-line-height-rule:exactly;font-family:'Open Sans', sans-serif;font-size:12px;text-decoration:underline;color:#18475d">View in browser</a> |
<a href="{unsubscribe_url}" style="-webkit-text-size-adjust:none;-ms-text-size-adjust:none;mso-line-height-rule:exactly;font-family:'Open Sans', sans-serif;font-size:12px;text-decoration:underline;color:#18475d">Unsubscribe</a>
<br />
</div>
</div>
</body>
</html>
You can use it how you see fit, but don't change the <title>{subject}</title>
mautic would automatically grab that for you.
Method 2
This is a mautic theme I just created out of the method one code, so, it is the same except that you can easily use it the way you would work with other themes in mautic.