How to display iCloud email by time?

I can set preferences in iCloud email on my PC so the email displays descending order based on time the email arrived or was sent. Why can't I do this on my iPhone4 and iPad2? There doesn't seem to be any rhyme or reason to the order of display. It's very hard to track emails when the most recent is randomly buried way down the list.

I've noticed there may be a pattern for these random placement for new email. I'm going to check it out in the future...

I'm thinking an incoming email on iPhone4 an iPad2 posts itself over/under (??) whatever email is highlighted. If I've looked at an older in-basket email, the next one in seems to be right by the one I was looking at.

Wirelessly posted (Mozilla/5.0 (iPhone; CPU iPhone OS 5_1 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Version/5.1 Mobile/9B176 Safari/7534.48.3)

Update: nope. Seems totally arbitrary. Makes it SOOO difficult to keep track of emails on the iPhone. Please Apple, what's the secret ... Or isn't there any?