The problem: after updating from NIS 09 to 10, OE6 is behaving abnormally. NIS10 re-configures OE creating a small "Yellow Envelope" in the Tool bar, it also creates an "Auto Generated AntiSpam Rule" (where in the subject line contains '[Norton AntiSpam]' and move it to the 'MFM' folder). Notice here that although it was automatically created, it chooses one of my folders and not the Junk (which does not exist in my case) or the one that it is supposed to be created by NIS10, "Norton AntiSpam Folder". Furthermore, the auto-generated rule cannot be edited or deleted; the two undelined selections do not have a hyperlink.
Cancelling the AntiSpam facility allows for this auto-generated rule to be edited or cancelled, only to be re-created as before.
Although the AntiSpam is working, it is treating my main folder as the AntiSpam folder. I would appreciate some suggestions. By the way, the chap that was helping me was unable to resolve the situation, even after re-installing NIS10.
I have found the solution before reading this answer and it is slightly different. As in your suggestion, I took step 1, 2, 3, 4 and 5 but in step 5 it did not create any AntiSpam folders, instead defaulted as before assigning a specific folder of mine as the AntiSpam bin.
As a second attempt I first created a new folder 'TEMP' and copied all of my messages from 'MFM' (this is the one acting as the AntiSpam folder) to it. Then re-named 'MFM' as 'Norton AntiSpam Folder', which by now was empty. Next, took all the steps from 1 to 5; yet again there was no creation of a new folder (I had previously created). Finally, I took step 6 and the automatic creation of 'AntiSpam Rule' was there and now working properly. Re-named 'TEMP' to 'MFM' and Bob is your Uncle.
Problem solved, but the root cause still to be figured out by the techies. Thank you for you help.
Upgraded from NIS 2009 to 2010 a week or so ago and antispam was working along happily until today when it decided to start routing spam to another folder. Norton AntiSpam Folder existed before the upgrade, and, until today, NIS 2010 was routing spam to it.
Tried the solution suggested by Kavitha but it did not work. Solution suggested by Tegus did work, however.