Recovering Old Emails

Hello,

I had been using Hotmail, then Gmail, for many years (when I made the switch to Gmail, all of my inbox got moved over). I now notice that for some reason, my oldest emails in my inbox are from March 2009, though I don't recall having ever deleted emails from before that time. I'm wondering if it's possible to recover emails from prior to 2009 that no longer seem to be in my Gmail inbox. Any help would be greatly appreciated as there are some very important emails I need access to.

Thanks you!