Index: wp-includes/user.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- wp-includes/user.php	(revision fcd674ca6c6dc26509c710b2996b304352340db6)
+++ wp-includes/user.php	(revision )
@@ -1211,10 +1211,22 @@
  * @return int|false The user's ID on success, and false on failure.
  */
 function email_exists( $email ) {
-	if ( $user = get_user_by( 'email', $email) ) {
+	if ( $user = get_user_by( 'email', $email ) ) {
-		return $user->ID;
+
+		/**
+		 * Filter whether the Email exists or not
+		 *
+		 * @since 4.5.0
+		 *
+		 * @param int|false $user_id Email user id.
+		 * @param string $email Email.
+		 */
+
+		return apply_filters( 'email_exists', $user->ID, $email );
 	}
-	return false;
+
+	/** This filter is documented in wp-includes/user.php */
+	return apply_filters( 'email_exists', false, $email );
 }
 
 /**