I've been seeing a few strange errors on one of my CiviCRM (4.4.4) site recently.
***ERROR*** Array ( [message] => Missing input parameters [code] => ) ... REQUEST_METHOD: GET QUERY_STRING: reset%253D1%2526jid%253D69%2526qid%253D1605%2526h%253D077ec51a7e598906 REQUEST_URI: //civicrm/mailing/optout?reset%253D1%2526jid%253D69%2526qid%253D1605%2526h%253D077ec51a7e598906 SCRIPT_NAME: /index.php PHP_SELF: /index.php REQUEST_TIME: 1428513094
Based on the error message, it looks like the optout request is somehow getting encoded, which yields a CiviCRM "Sorry but we are not able to provide this at the moment" error.
At first, I thought that there was a problem with the request, but I noticed that if I decode the request URI, I get a valid optout address.
It seems that there might be an email client out there incorrectly encoding the optout and unsubscribe tokens, but I haven't been able to reproduce this in testing both HTML and TXT email formats.
Any thoughts about what might be happening here?