Export mac mail emails to Microsoft entourage 2008

Question

I am looking for a way to migrate emails from mac mail to Microsoft entourage 2008. I am both these email clients in mac book air with mac os x 10.8.3.

So for I have gone through many other solutions available online, but non e was satisfactory. There are some very important emails that contains attachments having sizes in 60 to 100 mb. So how can I transfer these emails from apple mail to entourage 2008?