Troubleshoot message flags

You have selected multiple items. Reminders can only be set on individual items. Select each item individually and then set the reminder.

You are using Hotmail or another account type that doesn't support flagging messages.
The Quick Flag column has been hidden. To show it, on the View menu, point to Arrange By, and then click Custom. Click Other Settings, and then under Other Options, select the Show Quick Flag column check box.

You are not in a table view. Switch to a table view.
You are trying to flag an entire message conversation or thread. Only individual messages in a conversation can be flagged.

You have moved the item to the Deleted Items folder. Flagged items in the Deleted Items folder do not appear in the For Follow Up Search Folder.
You removed or cleared the message flag. If you are viewing the For Follow Up Search Folder, and you remove or clear the flag on the message, the item will disappear from the folder view. If this was your last action, you can add the flag back, and add the item back to your view, by clicking Undo Flag on the Edit menu. If this was not your last action, you will need to search for the item.

You added a message flag using Microsoft Office Outlook 2003 and then removed or cleared the flag using Microsoft Outlook 2002. Because different colored flags are new in Office Outlook 2003, only part of the flag information is removed by Outlook 2002 because it doesn't recognize the new information (iconID). When you view the item in Office Outlook 2003, the item appears to be flagged and will remain displayed in the For Follow Up Search Folder. To remove the flag information (iconID), using Office Outlook 2003, click the Flag Status column.
You have flagged a message header. This causes the entire item to be downloaded. You need to manually delete the message.