ok, found this in /includes/modules/tracking/swisspost.php
tep_db_query("insert into " . TABLE_CONFIGURATION . " (configuration_title, configuration_key, configuration_value, configuration_description, configuration_group_id, sort_order, set_function, date_added) VALUES ('Swisspost tracking GET url', 'TRACKING_GET_URL_SP', 'https://www.post.ch/EasyTrack/submitParcelData.do?domain=www.post.ch&defaultLanguage=de&reference=/swisspost-tracking&formattedParcelCodes=', 'Full GET url to call Swisspost''s tracking - DO NOT EDIT', '777', '0', '', now())");
but this is set to defaultlanguage=de
Even if I change it f.e. to =fr nothing changes.... any ideas ?