After upgrading to Outlook 2010 over a year ago, it became apparent that its junk email filter continued to work even after we disabled it.
It took so long for me to notice because I use Popfile to categorize the email I download from my ISP's POP3 server. Popfile would catch the most obvious spam before the Outlook junk email would process it.
But occasionally a message that Popfile marked as valid would end up in the Deleted Items folder. Outlook's occasional false positive would make me wonder what was going on, but it happened so rarely that it was easier just to check for these false positives than to research the issue. Besides, the corporate bulk mail filter running on the Exchange serve would stash things into the Junk Email folder, and I needed to check for false positives from that filter.
But then there was an incident that triggered an intra-departmental1 outcry about the issue. It was the day that several messages from our Content Management System got flagged by Junk Email and then deleted, causing folks not to notice updates on a few project files.
We all dutifully set Outlook's Junk Email filter to Disabled. But I continued to see valid messages from my ISP placed into Deleted Items. Recently I obtained a few spare moments2 and quickly found a solution to the issue. It was my favorite Outlook/Exchange website that I landed on. Here's the link:
The text says to change the value in a registry key, but in my case, the key didn't exist, so I created it, first.
Only time will tell whether this works. I will know for sure only if it doesn't. I suppose I can find an old message that triggered a false positive and send it to myself, but the header of that message would be different from the original header.
1 The emphasis is on the part of the word that contains "mental".
2 A good way to obtain spare moments is to schedule a meeting right after another meeting, so that if the other meeting runs late, the participants will be milling around outside the meeting room. After a while, you get a sense of which meetings will run the longest based on the topic and especially on whether certain coworkers will be in them. Some meetings can run so late that the folks who mill around will disperse and take an additional five minutes to reassemble, assuming they haven't gone off to lunch or embarked on an early vacation or retirement.