One of our users just came by and said she is getting an Out Of Office (OOO) message for every message she sends her boss, who is out of the office for a couple of weeks. The user swears it used to be the case that she would only get the OOO message ONCE. In Outlook 2010 on my computer, looking in File > Automatic Replies I see that just above the tabs for "Inside My Organization" and "Outside My Organization" it says "Automatically reply once for each sender with the following messages:" From this I infer that the user is correct in saying she should get the OOO message from her boss only once. Our Exchange server is v2010. If I log in to OWA I see the same verbage.
I have not used OOO for a very long time but it is my recollection that in the past it did only send the OOO message once for each sender, or maybe once a day, but the user is seeing the OOO message for each of several messages she sent to her boss today.