Some of my users are reporting receiving empty emails in their Outlook client. Only IMAP users are affected. Our email is hosted by Cox Cable. The only thing I can find in common with the messages is I believe they all had attachments. The message has no subject, no sender, no body, and the internet headers also show nothing. The time stamp and the size of the attachment is shown but when the message is opened nothing is there. However, if the user checks on their (Android) phone, the message looks normal. I checked the folder size of one user and the .ost was about 3.5 GB which seems reasonable. Users have sufficient storage space on the Cox server. I tried disabling the email scan feature of our Avast antivirus. I tried deleting the user's profile and recreating it. I tried uninstalling and reinstalling Outlook. None of these helped. Messages both from within and outside our company are affected. Any ideas? Thank you.