Index: wp-includes/formatting.php
===================================================================
--- wp-includes/formatting.php	(revision 27243)
+++ wp-includes/formatting.php	(working copy)
@@ -1989,15 +1989,14 @@
 		return apply_filters( 'is_email', false, $email, 'local_invalid_chars' );
 	}
 
-	// DOMAIN PART
 	// Test for sequences of periods
-	if ( preg_match( '/\.{2,}/', $domain ) ) {
+	if ( preg_match( '/\.{2,}/', $email ) ) {
 		/** This filter is documented in wp-includes/formatting.php */
 		return apply_filters( 'is_email', false, $email, 'domain_period_sequence' );
 	}
 
 	// Test for leading and trailing periods and whitespace
-	if ( trim( $domain, " \t\n\r\0\x0B." ) !== $domain ) {
+	if ( trim( $domain, " \t\n\r\0\x0B." ) !== $domain || trim( $local, " \t\n\r\0\x0B." ) !== $local ) {
 		/** This filter is documented in wp-includes/formatting.php */
 		return apply_filters( 'is_email', false, $email, 'domain_period_limits' );
 	}