Email Validator/Blocker

[ShawnK]

So I've used many differant email validators before but none had what I needed and that was to block free hosts...so here's my code

<?php

/**
* Shawn Kurtz
* shawnkurtz[at]gmail[dot]com
*
* Copyright (c) 2007 Shawn Kurtz
* Released Under Terms of
* GNU General Public License >= v2
*/

# [version]: 1.0.0
# [last_edit]: 06.30.07@01.39

/**
* @param  string $fEmail      the email address to check
* @param  bool   $fAllowFree  allow free email addresses(true/false)
* @param  array  $fFreeEmails array containing free emails to block
* @return bool                returns false on match/free email, true otherwise
*/
function check_email($fEmail, $fAllowFree=true, $fFreeEmails=array())
{
	if(empty($fFreeEmails) && $fAllowFree == false)
	{
		$fFreeEmails = array("yahoo.com", "hotmail.com", "gmail.com",
												 "inbox.com", "hotpop.com", "bigstring.com",
												 "mywaymail.com"
												 );
	}

if(preg_match("/^[a-zA-Z0-9._-]+@([a-zA-Z0-9].?)+[a-zA-Z]{2,4}$/", $fEmail))
{
	if($fAllowFree !== true)
	{
		$fDomain = explode("@", $fEmail);
		$fDomain = $fDomain[1];
		foreach($fFreeEmails as $fFreeEmail)
		if($fDomain == $fFreeEmail) { return false; }
	}
	return true;
}
else { return false; }
}

$email = $_POST['email'];

// you can call it like this, just using the email
if(!check_email($email)){ echo "INVALID EMAIL ADDY/HOST NOT ALLOWED!"; }

// or like this, you can block the default free hosts
if(!check_email($email, false)){ echo "INVALID EMAIL ADDY/HOST NOT ALLOWED!"; }

// or you can block your own set of domain names
$blocked_hosts = array("yahoo.com", "blah.com", "email.com");
if(!check_email($email, false, $blocked_hosts)){ echo "INVALID EMAIL ADDY/HOST NOT ALLOWED!"; }
?>

It blocks certain free hosts, please give me your feedback on the whole thing

[MarkR]

There are hundreds more free emails.

Also, your email blocks some legitimate domains. Remember that not all top level domains have less than four characters, e.g. .travel

So if I was [e-mail], you'd block my email.

In general, there's no point in validating email addresses particularly rigorously. If you really want, do a DNS lookup on the domain (although if the DNS fails with an error, the domain may still be valid of course).

Spammers and bad robots quite happily enter random valid-looking email addresses with legitimate domains on them.

Mark

PS: It seems that PHPBuilder.com's email address auto-highlight algorithm is as flawed as yours and mis-highlighted my valid email above.