Email regular expression

Question

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What is the best regular expression for validating email addresses?

I know this is a common question, but I still can't seem to find a great regular expression to use when validating email addresses.

I don't really have time to go read the spec and write my own. What have ya'll used before, and has it worked well? I don't really care about 100% matching the spec, but the closer the better.

Answer 1

^([0-9a-zA-Z]([-\.\w]*[0-9a-zA-Z])*@([0-9a-zA-Z][-\w]*[0-9a-zA-Z]\.)+[a-zA-Z]{2,9})$

This is an awesome tool to help write and check expression, not sure if you have it but hopefully its helpful.

Expresso

Answer 2

Plenty of info here.

Answer 3

Here's a function that I use. It does a little more than just run the email address through a regex, but so far it is the most complete solution that I found:

function validEmail($email, $skipDNS = false)
{
   $isValid = true;
   $atIndex = strrpos($email, "@");
   if (is_bool($atIndex) && !$atIndex)
   {
   $isValid = false;
   }
   else
   {
   $domain = substr($email, $atIndex+1);
   $local = substr($email, 0, $atIndex);
   $localLen = strlen($local);
   $domainLen = strlen($domain);
   if ($localLen < 1 || $localLen > 64)
   {
   // local part length exceeded
   $isValid = false;
   }
   else if ($domainLen < 1 || $domainLen > 255)
   {
   // domain part length exceeded
   $isValid = false;
   }
   else if ($local[0] == '.' || $local[$localLen-1] == '.')
   {
   // local part starts or ends with '.'
   $isValid = false;
   }
   else if (preg_match('/\\.\\./', $local))
   {
   // local part has two consecutive dots
   $isValid = false;
   }
   else if (!preg_match('/^[A-Za-z0-9\\-\\.]+$/', $domain))
   {
   // character not valid in domain part
   $isValid = false;
   }
   else if (preg_match('/\\.\\./', $domain))
   {
   // domain part has two consecutive dots
   $isValid = false;
   }
   else if (!preg_match('/^(\\\\.|[A-Za-z0-9!#%&`_=\\/$\'*+?^{}|~.-])+$/', str_replace("\\\\","",$local)))
   {
   // character not valid in local part unless 
   // local part is quoted
   if (!preg_match('/^"(\\\\"|[^"])+"$/', str_replace("\\\\","",$local)))
   {
   $isValid = false;
   }
   }

   if(!$skipDNS)
   {
    if ($isValid && !(checkdnsrr($domain,"MX") || checkdnsrr($domain,"A")))
    {
    // domain not found in DNS
    $isValid = false;
    }
   }
   }
   return $isValid;
}

The function has an optional $skipDNS argument that can be set to TRUE if you don't want to validate the MX records for the hos. Otherwise the function will attempt to validate that the e-mail address provided actually maps to a real email server.

It's useful to note that most RegEx email validation techniques will validate most e-mail addresses but they will most likely allow some carefully crafted invalid addresses or worst.. fail on some more obscure, but valid e-mail addresses. For more information you may want to check out the Internet Message Formats RFC which describes the allowed format for e-mail addresses.