We had a complete failure of our exchange server. After restore, most mailboxes/mail within those boxes work fine. Others, including my own, find old emails in our boxes that cannot be replied to. After checking outlook properties of the original sender of this bum email, it turns out that the Email Addresses tab for that sender is completely blank. Email received from that sender after the restore is fine, its just the pre-restore email that is affected. All email from that sender throughout my inbox (pre-restore) is affected this way. Only intra-company senders are affected, as all external emails seemed to have retained their SMTP addresses. There are at least 5-10 senders affected, I havent gone through my whole inbox to check each one. When I check these senders properties from the GAL, everything seems fine. Also, when checking the properties of the people who were sent To in the bum emails, their email addresses are still intact (unless they are one of the bum senders).