If you try a straightforward Ctrl+V afterwards, does it paste the correct clip?
This is my experience with an outliner (InfoQube) that uses Internet Explorer for it's text pane (html) - I'm not sure whose 'fault' that is.
I dont use Outlook myself so cannot confirm, but I'm wondering if it uses the IE engine as well for html text.
FWIW, I have no problem pasting in a forum I frequent that uses html formatting (not BBCode) - but I always use Firefox. (Just tried it in IE, the forum doesnt work properly there