If you've got several emails set up on your iPhone or iPad, you'll most likely want the ones you check most towards the top of your Inbox list. As of iOS 6 this is now possible. If you want your work email listed before your personal email, you can change the order in just a few taps.
Launch the Mail app on your iPhone or iPad.
Tap the Edit button in the upper right hand corner.
You will now see little move icons appear next to your mailboxes.
Hold down on the move icon next to the Inbox you'd like to change the position of. Now drag it up or down in the list.
Once you've finished reordering all your Inboxes, just tap the Done button in the upper right hand corner.
That's all there is to it. Your Inboxes will remain in the order you've put them in from now on.