+1  A: 

You are probably getting an error sending the mail, and that error is not being displayed. Try changing your error_reporting level:

error_reporting(E_ALL);

If that doesn't help and the page remains blank, if you have access to php.ini, check whether errors are being displayed and / or logged (display_errors and log_errors).

Pekka
I tried that, and it is still blank in firefox and the 324 error in chrome. The script doesn't send mail, just displays messages from the inbox.
Kp
Can you put a `echo 'test';` into the front of the script and see whether that outputs anything? Can you post the full script?
Pekka
The echo did not work. I posted the entire script.
Kp