This happens is you set the website "notification email" to your own address under your website's Main Options- this email is plain text and is designed to be parsed by 3rd party systems such as AWeber and is sent in addition to the normal HTML sale email that you receive from DPD.

To stop receiving the plain text notification email simply do the following:

1. Log in to DPD 
2. If you have multiple stores created, make sure you have the correct store picked at the top of the page
3. Click on Store Setup in the left menu 
4. Remove your email address from the Notification Email at the bottom of the page
5. Click on Save

This will turn off the plain text notification email.

The HTML sale notice email is controlled in your Profile under the Profile Menu in the top blue bar- there is a checkbox on this page to turn this global setting that applies to all sales in the DPD system on and off.