Validating if email address exists - php

Question

I'm a newbie in PHP. My goal is to send an email to the user registered in my system.
Here is my code:
$msg= " Hi $gen./$lName, copy and paste this code in order to activate
your account copy and paste this code:$num" ;
$email = "$emailadd";
$name= "GoodFaith Network Marketing Inc.";
$subject = "Account Activation";
$message = wordwrap($msg,70) ;
$sender = "cjoveric#myalphaedge.com";
$mail_header="From: ".$name."<". $sender. ">\r\n";
$sendmail=mail($email, $subject,$message, $mail_header );
I was able to send an email, but my problem is I want to know if the user's email address exists in Yahoo, GMail or other mail services.
Is there any way I could filter out invalid emails?

Answer 1

Use SMTP mail the best and easy to use SMTP.
$mail->IsHTML(true);
$mail->From="admin#example.com";
$mail->FromName="Example.com";
$mail->Sender=$from; // indicates ReturnPath header
$mail->AddReplyTo($from, $from_name); // indicates ReplyTo headers
$mail->AddCC('cc#phpgang.com.com', 'CC: to phpgang.com');
$mail->Subject = $subject;
$mail->Body = $body;
$mail->AddAddress($to);
if(!$mail->Send())
{
$error = 'Mail error: '.$mail->ErrorInfo;
return true;
}
else
{
$error = 'Message sent!';
return false;
}

Answer 2

Not really. About the best you can do is send an email and see if the user responds to it.

Answer 3

Doing a regex check on email address can be frustrating for some users, depending on regex. So, I recommend to skip your regex test and just send the verification email with a confirmation link -- anything else will leave your application brittle and subject to breakage as soon as someone comes up with a new DNS or SMTP extension. It's best to get that dealt with when their paying attention.
For example:
-a confirmation code that needs to be filled in your website
-a link, going to your website, that needs to be visited
And still it is uncertain whether the email is existing afterwards, as it is easy to simply create a temporary email to pass the validation and delete it afterwards.
Instead of validating email addresses you can use the Google API to let your users sign in using their account. It is also possible to use OpenID on a similar way. Though, even this is not 100% perfect. But heay, nothing is 100%. We all try to make is work as we want as much as possible. That's it.
PS: ICANN is expected to approve UNICODE domain names Real Soon Now. That will play merry hell with Regex patterns for email addresses.