Is it failing to reach your users specifically on AOL or is it failing on other mail hosts also?


[php]require_once "Mail.php";[/php]

What mail class are you using? Does it check for mail injection? If it doesn't, your php allows for mail injection. This would be the cause of your mail being blocked because its being used by others to send spam..
You should always escape any new lines from mail headers such as:

[php]
$from = $_POST['client']." <".$_POST['email'].">";[/php]



The PHP docs on the mail() function also have a few pointers on how not to get your emails in spam folders. see: http://www.php.net/mail