(No Sender) coming up in my search in mail
When I search in mail a lot of the emails that come up are from (no sender)? The emails themselves just contain all the text in a jumbled format from an actual email. Sometimes half the search results are these (no sender) and it makes it difficult to find what I'm looking for. Any idea on how to get rid of them. I'm running ElCapatain 10.11.3 on a 5k iMac.
iMac with Retina 5K display, OS X El Capitan (10.11.3)