--- common.inc	2004-12-30 16:00:00.000000000 +0100
+++ common.inc.new	2005-01-08 14:50:13.857500000 +0100
@@ -530,7 +530,7 @@
 /**
  * Verify the syntax of the given e-mail address.
  *
- * Empty e-mail addresses are allowed. See RFC 2822 for details.
+ * Empty e-mail addresses are not allowed. See RFC 2822 and RFC 1035 for details.
  *
  * @param $mail
  *   A string containing an email address.
@@ -539,7 +539,13 @@
  */
 function valid_email_address($mail) {
   $user = '[a-zA-Z0-9_\-\.\+\^!#\$%&*+\/\=\?\`\|\{\}~\']+';
-  $domain = '(?:(?:[a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]*[a-zA-Z0-9])\.?)+';
+
+  $letter = '[a-zA-Z]';
+  $letterdigit = '[a-zA-Z0-9]';
+  $letterdigithyphen = '[-a-zA-Z0-9]';
+  $domainpart = "$letter(?:$letterdigithyphen*$letterdigit)?";
+  $domain = "(?:(?:$domainpart\.)*$domainpart)";
+
   $ipv4 = '[0-9]{1,3}(\.[0-9]{1,3}){3}';
   $ipv6 = '[0-9a-fA-F]{1,4}(\:[0-9a-fA-F]{1,4}){7}';