Gmail & Outlook 2007 (Flagging Gmail in Outlook creating 4 tasks)
I recently setup my gmail/imap account in outlook 2007. When I flag an email for follow up, it creates 4 copies in my task menu of the same item. When I check off the flag from one of the messages, all four go away. Why the copies? What can I do to minimize this?
The cause of this is the implementation of IMAP folders/labels that Google uses. I tested this behavior and in my case Google also attached the "starred" and Important labels to the message with the flag (I am not sure if this happened when I flagged it or not). This creates 3 instances of the message in Outlook: one in the Inbox, one in "starred", and one in Important. Each one of these instances has a flag, and so there are 3 instances in the To do list. In your case you likely have 4 labels on it, which makes the 4 flags. You can find these Gmail specific folders if you expand the [Gmail] folder in the folder list (example pic is from Outlook 2013).
If you look at the detailed view list of tasks, it should show you the folder the flagged item is in.
In terms of how to address this issue, right click the folder list and choose IMAP folders. In there you can unsubscribe to specific folders. You can then remove the folders that are Gmail specific. There may also be a box to check which reads When displaying hierarchy in Outlook, only show subscribed folders. You should check that as well.