I recently switched to Mail.app from Outlook 2011 and have been importing some of my archive messages. The problem is that for many of the messages, Mail.app seems to think they are duplicates so it only shows one of them. However they are NOT duplicates, they are not even close. All the messages are there, I can search in spotlight for them, however if i want to scroll through a folder they will not show up. I can see certain messages have a '8 Duplicates' or similar written on the top right corner, and when you click that all the messages show, but it is only temproary, as soon as you move to a different folder and then come back all the messages are hidden again.
How can I turn this off? And any ideas why Mail.app thinks the messages are duplicates? they are on different dates, different subjects, 100% different as far as i can tell.