MAMP is a really handy to test PHP site locally.
But you don't get mail support in the free version. Unless you follow the tip here:
http://www.mattdipasquale.com/blog/2009/05/27/how-to-send-email-with-ma…
Basically tell postfix to use your ISP smtp server
This works and is REALLY easy! And can be undone later. It's just editing a text file. I know it's scary and advanced (I was scared and confused at first), but just do it. It's fine. And if it doesn't work, you can change it back. Simple! :)
Shutdown MAMP completely
Edit /etc/postfix/main.cf
Search for "relayhost"
Add relayhost = smtp.example.com
Start up MAMP again