How do I stop my facebook picture being visible in sent emails?

I do not want a profile picture. I have eddited my profile and currently it has no picture. When I am in my outlook inbox or writing an email there is no picture, just as I want. However, whenever I go in to my 'sent' emails they all display the picture from my facebook account on my profile. As my outlook profile has no picture there seems to be no way for me to remove this? Can someone please tell me how to unlink my facebook from outlook (I do not recall ever linking them so not sure how it happened) and how to make sure that the emails I send do not have any picture for me? Thank you in advance.