Question about Outlook Express

I was looking through my e-mail this morning for a specific e-mail sent within 2009 and 2010. However, upon reaching the beginning of 2010, there were apparently no more e-mail messages. I tried checking through all the folders, and any messages previous to 2010 that I had placed into another folder were still there, some as far back as 2002. However, the inbox only went back as far as 2010. There has been no point since the creation of this account that I have not logged in within the requisite 270 days, which is evident by the fact that I still have older e-mail messages, just not in the inbox. I looked to see if there was any sort of automatic deletion from the inbox that was instituted by Microsoft at any point and was unable to find it. I understand that doesn't preclude the possibility that said automatic deletion exists, but if it does exist, I was never informed. I am looking for someone to either explain why this happened (and not in vague "could have" terms, but PRECISELY why) or, and this is my preference, get those e-mail messages back. Also, if there is an automatic deletion process over time, I request the easiest way to migrate all my e-mail to GMail, because I will most certainly not support any sort of automatic deletion process save from the Deleted folder.