Calibre not sending to Kindle

Hi,

I am having trouble setting up Calibre so that it sends news to may Kindle paperwhite. I have set up my kindle email address and my email - this seems to be working as I can receive the test email. However, it seems like news are not delivered to my Kindle: Calibre reports them as correctly sent, but they are nowhere to be found on my Kindle.

Any ideas on what I might be doing wrong?

Many thanks