iTunes tells me it can't sync data to my iPhone because of an "error remapping record identifiers." What can I do?

Numerous iPhoneFAQ readers have reported that iTunes will fail to sync data to their iPhone while reporting the cause as an "error remapping record identifiers." Though this error most commonly happens when trying to sync mail, it has also been reported during attempts to sync calendar and contact data as well.

This quick and easy fix works well for the vast majority of users:

Open iTunes, disable mail (or whatever the failed sync type is) syncing, apply, close iTunes.

Now reset your sync history:
On Mac: Open iSync (Finder -> Applications - iSync). Go to Preferences and choose "Reset Sync History".
On Windows: Open iTunes and choose Edit -> Preferences. Select the Sync tab and choose to reset sync history.

Open iTunes, enable mail (or whatever the failed sync type is) syncing, apply, sync.