Exchange mail doesn't see new Emails in subfolder

RobotFans,

I have several new email messages in a subfolder (Lezen).
But somehow the Robot doesn’t see them and thus doesn’t process them.

I have tried all kinds of settings with the subfolder
\Inbox\Lezen
\inbox\Lezen
..\Lezen
\Lezen

But now i’m out of options.
Is there someone with the golden tip?

Regards
Marcel