Apropos of this "missing emails" business, Dan Froomkin went ahead and asked a White House spokesperson what the actual rules on sending email were for staffers. Here's the response:

But when I asked Stanzel to read out loud the White House e-mail policy, it seemed clear enough to me: "Federal law requires the preservation of electronic communications sent or received by White House staff," says the handbook that all staffers are given and expected to read and comply with.
"As a result, personnel working on behalf of the EOP [Executive Office of the President] are expected to only use government-provided e-mail services for all official communication."

White House officials are now claiming it was an accident that Karl Rove and friends were using outside email accounts, because there was just so much confusion about the rules, and how was Rove supposed to know that those deleted emails would just up and disappear? But, of course, the email policy's perfectly clear, Rove's not a third-grader, and he's certainly old enough to know that he wasn't following the handbook (which, incidentally, the White House refuses to make public).

--Bradford Plumer