First off, it is OOF, not OOO. It is Out of Facility, not Out of Office.
A few days ago, I received a request asking me why people were getting the OOF from a user that was out, even though they had received it already. In other words, you are only supposed to get the OOF response once during the time frame, so why were people getting replies every single time.
At first, I thought somebody just set up a mailbox rule, rather than using the Automatic Replies option. After checking the mailbox, I saw that the Automatic Replies was set correctly. After a bit, I remembered some peers talking about this issue, and I found the article. Thank you Bing.
Summary, the history of responses is tracked, and there is a limit of 10,000. I still can’t believe that this limit was actually exceeded. In this case, it was a user that gets hundreds of emails a day, and they were out on medical leave for almost three months.
I am shocked that it happened. I am even more shocked that I remembered that this was an issue and found the article.