I have a number of rules that filter mail to my deleted items folder. Sometimes it seems a rule applies to a message which I did not intend it to apply to. How can you "debug" which rule applied to a given message?
One fairly low impact way might be to change the rule actions to do it's usual thing to the messages (such as move them to a folder) and add a category to them.
Create a category for each rule you might need to debug (or all of them), then for any given email you can quickly see which rule(s) have been applied to it by checking the categories. I would suggest setting the colour of all the categories used for this purpose to the same thing, such as a very neutral pale grey.
I am not sure exactly how much infomation you can pick out of outlook's logging feature, but it might help. I just enabled this on one of my machines and going to see if it shows me my rules in action. To enable the logging:
Under the Tools menu, click Options.
On the Other tab, click Advanced Options.
Check (enable) or uncheck (disable) the Enable logging (troubleshooting) box.
Click OK twice and restart Outlook. Logging Enabled should appear in the title bar.
This applies to outlook 2007. The log file is created at C:\Users\user name\AppData\Local\Temp\Outlook Logging\OPMLog.log in Windows Vista. For Windows XP users, it will be created at C:\Documents and Settings\user name\Local Settings\Temp\Outlook Logging\OPMLog.log
You can try disabling all the rules, moving a message that was affected back to the Inbox, then running one of the possibly-problematic rules on the Inbox to see if it does anything to the message. If not, then try again with one of the other rules. Kind of a clunky debug, but it should help to identify while rule is the culprit.
I had 20 rules all sending email to the Deleted folder. Some important email was getting nuked.
I created 7 Deleted folders (deleted1 ... deleted7), modified all rules that deleted emails, assigning them randomly to one of the seven folders, with between2-4 rules per folder.
Then I cleaned up the deleted folder, deleting email I knew I didn't need, leaving email that I might refer back to and restoring good email to Inbox. Then I selected all rules and ran them against my Inbox, checked which folder got the emails I didn't want deleted and that narrows it to 4 rules, then move other rules back to Deleted folder, spread the four rules across folders, re-run. Bam, done.
I like the coloring idea (move to deleted folder AND assign it to this category / color), I just didn't take the time to learn to implement it.