This is a problem I've had for quite some time. We have an Exchange server and I'm using Mail in Mavericks for my email. If I receive an email with an attachment on my Mac Pro at work, attachments are downloaded. However, when I open Mail on my Mini at home later that day, the attachment isn't included in the email. It happens the other way, too. Open it first on the Mini at home and the attachment is included. But open it later on the Mac Pro at work and there's no attachment. If I log onto the Exchange server with Safari, the attachment is still with the email. I can manually download it, or forward it and the attachment arrives. Does anyone know why the second opening of an email fails to have the attachment?