diff --git a/wp-mail.php b/wp-mail.php
index 6775de8a27..aa062c6874 100644
--- a/wp-mail.php
+++ b/wp-mail.php
@@ -14,6 +14,12 @@ require(dirname(__FILE__) . '/wp-load.php');
 if ( ! apply_filters( 'enable_post_by_email_configuration', true ) )
 	wp_die( __( 'This action has been disabled by the administrator.' ) );
 
+$mailserver_url = get_option( 'mailserver_url' );
+
+if ( 'mail.example.com' === $mailserver_url || empty( $mailserver_url ) ) {
+	wp_die( __( 'This action has been disabled by the administrator.' ), 403 );
+}
+
 /**
  * Fires to allow a plugin to do a complete takeover of Post by Email.
  *