Hello carreragt1990 & welcome
If your Hotmail account is a relatively newish one, and by newish I'm not able to say exactly when Microsoft made this change, but if it's about 4 odd years old, then this is why you can't link it to Mail.app. It's only the old Hotmail accounts that work with HTTPMail Plugin.
There is also a chance that you didn't configure the settings properly too .... my HTTPMail Plugin works fine with only the oldest of my 2 Hotmail accts.
Did you follow the instructions to the letter? It's been a while since I set mine up but you need to follow the instructions very carefully, and the only way to uninstall the plugin is to follow the instructions on the installation manual ... I think the uninstall procedure is right at the very end of that document.
Are you using Tiger or Leopard? I'm pretty sure the Leopard version is working but I'm still using Tiger. The version I have installed is Version 1.49 ...