I have a user who recently has been noticing a problem. A very very few of her incoming emails will go right to her Deleted Items folder instead of the InBox. She had two today. They were about the same subject, so the subject text was the same, but one was an internal email and one external. I looked for the obvious things and here's what I found:
1. Not running in cached exchange mode
2. Junk filtering not turned on and no blocked senders, plus 99.9% of email from the internal users always is routed properly.
3. No rules in her Outlook.
4. She is not simultaneously logged into another computer.
5. She doesn't use OWA
6. She doesn't have a smart phone or iPad
7. AV is installed, but if it found an email it didn't like it would quarantine it and NOT put it in her Deleted Items folder, plus I'd get an alert from the AV product.
8. No Spam client on the user's PC
9. I tried sending her an email with some of the same text in the subject line and it went to her inbox properly.