I'm in the process of fixing the last of the email folders using that temp folder trick. Soon the only problems left will be the inadequacy of the iPhone's Mail program.

Just to make sure I'm not seeing some random issue, can you confirm that your SENT folder on the iPhone shows only your OWN (from) address instead of the address of your recipients? I can't get over that since I've clearly defined that folder as the "sent" folder using the prefs on the iPhone.