Mac Mail issues

I have been using the standard Mac Maill app since I got my macbook and it's not acting up in a really weird way. I can't send an email and instead on the "send" button in the top left corner of a "new message" window it says "chat with recipients". Sometimes it goes back to normal but it's making me go crazy. I use a @hotmail.com address and OS X 10.6.8
Might this has anything to do that Hotmail has switched to Outlook and some settings has changed?

 

I thought of that, but that doesn't seem to be the problem.
Sometimes it's "send" and sometimes is "chat with recipients".. it changes with different recipient...