I am using EE's built-in Mailing List Activation Instructions email to send out an html templated email to users who signs up on the website's newsletter. The email is sending perfectly, but instead of displaying the rendered html template and content, it shows the html code directly onto the email client. Please see below. 

![MS Outlook Displaying HTML Code](https://i.stack.imgur.com/x3TTb.png)

It does the same with Gmail. I have set the default email type in the backend as HTML, but does not seem to take effect.

Is there perhaps anything I am missing or doing incorrectly maybe?