If not all duplicates were found, then they're probably not duplicates, but just similar objects. But they can be removed, too.
The easiest way to repeat the search. If the program can't find 100% identical objects, it will (within limits) suggest to remove similar items. However, it will do this only as long a safe, automatic recognition is possible.
If that's not enough:
|•||Please choose 2 similar items|
|•||Select both items in Outlook (CTRL key + mouse click)|
|•||Use "More > Compare 2 objects..."|
Now you can see, what properties are identical / different. If you think, that the program should recognize this, please use the button to send us a copy.
Adapting the scan to your duplicates:
Please use "More > Advanced Scan" to choose properties should be compared.
Special case 'Newsletters':
If you're receiving a newsletter twice, usually two things are different: The recipient and the URLs that you can click on. To track your behaviour they often contain personalized ids. It is not possible to recognize duplicates with such a different e-mail body.
The program cannot remove duplicates with really BIG differences. Like the same subject in different languages.