Index: wp-includes/pluggable.php
===================================================================
--- wp-includes/pluggable.php	(revision 5744)
+++ wp-includes/pluggable.php	(working copy)
@@ -167,8 +167,10 @@
 		$phpmailer = new PHPMailer();
 	}
 
-	// Compact the input, apply the filters, and extract them back out
-	extract( apply_filters( 'wp_mail', compact( 'to', 'subject', 'message', 'headers' ) ), EXTR_SKIP );
+	apply_filters( 'wp_mail_to', $to );
+	apply_filters( 'wp_mail_subject', $subject );
+	apply_filters( 'wp_mail_message', $message );
+	apply_filters( 'wp_mail_headers', $headers );
 
 	// Default headers
 	if ( empty( $headers ) ) {