Removing the facebook avatar from appearing in messages I send to other users

My problem is that an avatar photo from someone else's facebook profile (completely unrelated to me) shows up as my own. I don't have any connections setup to facebook in my account. I tried adding my own avatar, however the facebook avatar still shows up when I sent a test message to another outlook / hotmail account I have. I've also disabled showing public content from 3rd party networks - but it only disables the avatar for that one account. Any outlook account with that setting enabled still can see the facebook avatar. Any way to remove the avatar from appearing completely?