I'm on a corporate exchange server. Have a Lumia 928. Periodically, all messages in my in box disappear, and the in box resyncs from scratch, repopulating the outlook inbox. Emails aren't deleted on my corporate email or office computer, just on the device. Download email from is set to 2 wks, and do notice that in box has 990+ emails when it repopulates. IT has checked event logs each time and see nothing. Sometimes it happens every few days, and other times, a week or more goes by. Plenty of storage on device. I set download from to 7 days a few days ago, and hasn't happened again, but am expecting that it will, but 7 days email is less than ideal. What do folks think?