Sorry, I should have been clearer. I'm pretty familiar with how my ipad works. There appears to be a legit bug with the software, at least for some users. When I load mail, sometimes it's stuck in one orientation, even if the rest of the ipad apps are able to rotate freely. I don't always notice it because sometimes the ipad is oriented in the same direction as mail, but other times it's not and when you start the mail app, the screen loads upside down. Switch to another app, back to right side up and so on. You have to either turn the ipad over, or kill the mail app by double tapping the home button and ending the program from the list of running apps.
After you do that, the mail app starts to rotate again normally when changing the orientation of the device. No reset is required, by the way, as is posted above - at least on mine. Killing the app alone is enough to 'fix' the problem.
I've seen a number of posts where someone posts the 'fix' as a solution to this issue, but I don't consider it a reasonable resolution. Even if killing the mail app works, the problem just comes back a week or two later, very randomly. So then you end up having to do the 'fix' over and over again whenever the mail app flakes out.
So, I'm wondering when Apple is going to actually fix this issue.