made is primary not required.

Civi/DataProcessor/Source/Contact/EmailSource.php

@@ -30,18 +30,6 @@ class EmailSource extends AbstractCivicrmEntitySource {
     return 'civicrm_email';
   }
 
-  /**
-   * Returns an array with the names of required configuration filters.
-   * Those filters are displayed as required to the user
-   *
-   * @return array
-   */
-  protected function requiredConfigurationFilters() {
-    return array(
-      'is_primary',
-    );
-  }
-
   /**
    * Returns the default configuration for this data source
    *