Yes, the hot water will have turned into ice faster. This oddity, known as Mpemba effect after Erasto Mpemba, a Tanzanian student who prominently noticed it, is a bit of a mystery. It might have to do with evaporation, or salt crystals that lower the freezing point of already cold water as it cools further but which precipitate in hot water and have no influence on the latter's freezing.
Either way, here's how to turn cool mail in mbox format (from Mozilla Thunderbird, for example) into hot mail in .eml format (to be used with Outlook Express) really fast:
›› mbx2eml converts messages from mbox files (used by Mozilla Thunderbird and other email programs) to .eml files (which are easily imported into Outlook Express) reliably and with utmost simplicity. (Windows)