I have 56 messages in my Main folder that do not contain my address anywhere in the headers. They are all addressed to one of my associates whose mailbox I will add to my folder list as an added mailbox. It appears that his unread mail is ending up in my Main folder. I have asked him if he remembers receiving some of them and he doesn't.
I'm posting to the list and the community forum because I believe this to be a serious problem if it can be confirmed.
I have some cleaning up to do before I can test to see if I can duplicate. I may have broken my test conditions though because before figuring out that the messages weren't mine I went through all of my identities and, in a few of them, turned on the option to allow read mail to stay in the NMF.