Gw 8.0.2 Window Server 2008r2 cluster.

I have a user who sends out reoccurring appointments from time to time. When he deletes the acceptance emails it also deletes all of his email for a 10 day period. The last time he did this it deleted all email from Jul 13 - 23. The email he intended to delete was in his trash, however the other email was nowhere to be found. Any ideas on what could be causing this? He swears he is deleting the email 1 at a time as they come in.