Index: pluggable.php
===================================================================
--- pluggable.php	(revision 12162)
+++ pluggable.php	(working copy)
@@ -374,7 +374,9 @@
 	$phpmailer->FromName = apply_filters( 'wp_mail_from_name', $from_name );
 
 	// Set destination address
-	$phpmailer->AddAddress( $to );
+	foreach ( (array) $to as $recipient ) {
+		$phpmailer->AddAddress( trim($recipient) );
+	}
 
 	// Set mail's subject and body
 	$phpmailer->Subject = $subject;