How do I stop MS Outlook from formatting my entire email when I only want to format my selection?

I'm having trouble with Outlook formatting my entire document with whatever I select (Bold, Italics, even bulleting!) For example, if I have a several lines of text (with paragraph returns) and I want to bullet a couple of lines in there. I highlight the lines, and hit the Bullet icon. Then the ENTIRE document (even empty paragraph returns) are bulleted. If I hit undo, then Outlook removes the bullets except for the line that I had highlighted in the first place. It's almost like a universal formatting that I can't get rid of. Can anyone help me?
How do I stop MS Outlook from formatting my entire email when I only want to format my selection?
highlight only certain parts