Some DROID owners on the Verizon forum are complaining that the DROID has a bug that is deleting their corporate email. Even starting over and setting up the mailbox again is not helping. Calendars and contacts are not affected. One possibility is that this is related to the Taskiller app that closes open applications to save battery life and memory. According to one DROID owner posting on the board, if you have downloaded the app from the Android Market, long press on the email application and hit “Exclude”. Whether this solves the problem is still unclear. But so far, the problem seems limited to corporate email accounts. Let us know if you have had this problem and what solution you have found that works.
source: VerizonForums via ubergizmo