Determine if Email Address Exists

[random1]

How can you determine if a email address exits?

 

Can PHP be used to ping a mail server to determine if the email address exists?

[doni49]

That's one of the favorite tricks of spammers--brute force pass a bunch of addresses to mail servers in hopes of finding valid addresses.

 

For that reason a lot of mail server administrators have config'd the server to NOT tell whether or not the address is valid.

 

What exactly are you trying to do?  Validate an email address in a form?

 

Your best bet would be to just check and see if it follows the proper format.

 

Here's what I use for that.

 

        $email = true;
// Check for an email address.
if(!empty($_POST['email'])){
	if (eregi ("^[[:alnum:]][a-z0-9_.-]*@[a-z0-9.-]+\.[a-z]{2,4}$", stripslashes(trim($_POST['email'])))){
		$e = escape_data($_POST['email']);
	} else {
		$validForm = false;
		echo '<p><font color="red" size="+1">Please enter a valid email address.</font></p>';
	}
}else{
	$email = false;
}

 

 

[darkfreaks]

<?php

if( !preg_match( "/^([a-zA-Z0-9])+([a-zA-Z0-9\._-])*@([a-zA-Z0-9_-])+([a-zA-Z0-9\._-]+)+$/", $email))
 {
   return false;
 }     

 // gets domain name
 list($username,$domain)=split('@',$email);
 // checks for if MX records in the DNS
 $mxhosts = array();
 if(!getmxrr($domain, $mxhosts))
 {
   // no mx records, ok to check domain
   if (!fsockopen($domain,25,$errno,$errstr,30))
   {
     return false;
   }
   else
   {
     return true;
   }
 }
 else
 {
   // mx records found
   foreach ($mxhosts as $host)
   {
     if (fsockopen($host,25,$errno,$errstr,30))
     {
       return true;
     }
   }
   return false;
 }
}
?>