Vacation filter (Round Cube)

==== Required information ====
- iRedMail version: 0.8.4
- Store mail accounts in which backend (MySQL):
- Linux/BSD distribution name and version: CentOS 6.4
- Related log if you're reporting an issue:
====

I'm trying to figure out how to use the vacation filter. I have enabled it and yet it doesn't send a reply message out. Is there anything else I'm required to configure? Or, is there another way of enabling it?

Thanks,
Neil