Description: ------------ When an email address such as '"John Doe\\" <text@example.com>' is passed to RFC822 to be validated _hasUnclosedQuotes() is detecting the '\"' at the end of the string and presumes that the quote has been escaped. Because it only finds a single opening quote it presumes that the string has unclosed quotes and thinks that the email address is invalid. Test script: --------------- <?php require_once("Mail/RFC822.php"); require_once("PEAR.php"); $addresses = array( array('name' => 'John Doe', 'email' => 'test@example.com'), array('name' => 'John Doe\\', 'email' => 'test@example.com') ); for($i = 0; $i < count($addresses); $i++) { // construct the address $address = "\"".addslashes($addresses[$i]['name'])."\" ". "<".$addresses[$i]['email'].">"; $parsedAddresses = Mail_RFC822::parseAddressList($address); if(PEAR::isError($parsedAddresses)) { echo $address." :: Failed to validate\n"; } else { echo $address." :: Parsed\n"; } } ?> Expected result: ---------------- "John Doe" <test@example.com> :: Parsed "John Doe\\" <test@example.com> :: Parsed Actual result: -------------- "John Doe" <test@example.com> :: Parsed "John Doe\\" <test@example.com> :: Failed to validate