I have the same issue. I recently noticed that the sender name would look like this: .JaneDoe

I never noticed the dot in front of sender names before. When I click on the name there is no e-mail address. Occasionally when replying to these -emails the recipient does not receive anything. But I reiceve no prompt like 'mailer-deamon' that the e-mail was unsuccessful. I didn't have this issue a few months ago. Is it an update? I suspect these e-mails come from people using cell phones. Perhaps that has something to with it?

All emails that comes to you should have return addresses; unfortunately, Outlook via the Exchange Server hid those addresses from you. This is my biggest problem with Outlook. I decided to export all my Outlook emails to Windows Live Mail and the problem went away; every single email I have, I can see the email addresses of the sender. I love Outlook, but that is a deal breaker for me. I hope you are able to find a solution.