Give some details on your mail setup. What kind of web server are you using? and is smtp set up on that server, or are you trying to relay through another smtp server?
Also make sure all your mail content is in the same variable.
$mailcontent = "Customer name:".$name."\n";
$mailcontent .= "Customer E-mail:".$email."\n";
$mailcontent .= "Customer Comments:".$feedback."\n";
In your From, remove the space before the colon:
$fromaddress = "From: Something@yahoo.com";
And you might first attempt the mail function without the 4th arguement, that will send the message using the web servers defaults and will be easier to troubleshoot the servers mail config...if your message is successful, then you can mess with the headers.
mail($toaddress, $subject, $mailcontent);