By default there are a couple of OOO intercepters that will trigger/catch OOO replies, these look for the following strings:
(out of office)|(autoreply)|(auto-reply)|(auto reply)
However, if you are seeing messages get past these interceptors, I would recommend submitting a case in your customer group here in the Jive Community as a next step where a member of our support team can assist in modifying these interceptors. When you submit the case, if you could provide a couple of example OOO emails that made it though this should help them make the updates.
Any thoughts on Tracy's comment:
<snip> Please note: As far as I know, this still only keeps out of office messages from posting to the community. It does not address people who have created content from getting the out of office messages delivered to them in their own inboxes. Don't think there is a good way around that.</snip>