Double image shown on Post?

I email an image and text to Postie and specify a specific category. I have a WP menu item defined as Category so I can click on that and get a listing of all the posts in that Category on one page. The issue is the page shows both the main image and a thumbnail image.
Use first image as Featured image = Yes
Include Featured Image in Post = Yes
I believe on an early email I set Thumbnail to yes, does this setting remain until I turn it off in another email?

In this sample the first post was entered through WP, not Postie.

http://www.nwirestore.com/nwirestore.org/category/firstg/

Thanks Wayne, your helping Habitat for Humanity..

https://ww.wp.xz.cn/plugins/postie/