I have changed the default and contact email address in my admin options and I don't receive anything from any method from anyone on my forum. Is there another thing I need to change or am I missing something?
Is the email address valid?
Is the domain being used blacklisted (or the MTA's IP) so that the mail is going into spam?
Simply changing those two options should not have effected anything, but I have a feeling one of the above is coming into play.
Check your domain and your server IP at http://mxtoolbox.com/blacklists.aspx.
Your email sending service (SMTP or the PHP default method which hands off to a program like Postfix) could potentially be changing behavior based on the "from" address and not allowing it if it doesn't match what's expected. Are you seeing any server errors logged in the control panel? What mail sending method are you using?