It's very interesting to see many ppl have problems with it.
There are two or more settings for auto responder:
1. This is per email queue.
Enable New Issue Autoresponder?
If enabled, the system will send an Autoresponder message confirming the receipt of a new issue.
2. From staff panel, property of user group.
Option: Should Send Ticket Autoresponder
I'm not sure if that's all, anyway, autoresponder doesn't work as what I expected. Sometimes it didnt send, sometimes it send with a old responder template, sometimes it sent correct responder. I'm totally confused.