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Tip for users of Opera's email client

If you've been using M2, the email client coming with Opera, for a while, you may find that the "learning" spam filter's performance, after initially improving, starts trending downhill, leaving more spam messages unfiltered. I was puzzled by that, but I think I've found the cause: backdated spam.

In traditional, non-learning spam filters, spam sent out with a date earlier than it was posted is a bit of a nuisance, but it either gets filtered or not, and that's the end of it. However, if a backdated spam message bypasses a learning filter, and you don't spot and correct it because it's listed high up in your list of email messages (or, if you've got M2 configured not to show messages more than a certain age in the Unread folder, not shown at all), the filter then learns that that message was not spam. The filter will then use that knowledge to determine that similar messages are also not spam, and if these aren't corrected either, the number of false negatives will slowly creep up.
So if your spam filter begins to let you down, start hunting down those hidden spams. Go to the Received folder. Then, in the View menu, uncheck all options under Show and set the period to Forever. That way, you have a duplicate of your Unread folder, without any messages you already know for certain aren't spam. Then scroll/page up, and look for messages that are still marked as new, even though from the date they would seem to be months old. It often helps to change the display order, so you get a fresh look at the list. Those old/new messages are very likely to be spam, but you be the final judge of that. Mark them as Spam if they are. When you're done, reset your Received folder to its normal settings. That should improve the filter's ability to recognise spam, at least for a while.

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This page contains a single entry from the blog posted on January 1, 2005 9:49 PM.

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