Apple Mail "Send" button not working

Is anyone else having a problem with their "Send" button in Apple Mail not working? The only way I can send any emails is to either add a return at the end of all my emails for it to then send. If I'm trying to send an internet link the only way it will send is if i right click on my mouse and then it will all of a sudden send. Soooo frustrating. I've tried everything (including reinstalling my accounts, rebuilding, restarting, etc) and nothing will fix the problem.