Found it ! (^_^)
in the log, it says "The specified path, file name, or both are too long"
So I un checked the box "Create folder tree based on each email" but still doesn't work. lol
Now the error is "Failed to save email, ex: Could not find a part of the path..."
Seems that it still try to same in a folder free for the email (note that it did work for the attachments)
NB: the Yen symbol is normal: we are in Japan (don't ask me why Japanese people want to us "¥" instead of "\" lol. )
FYI, the lines in the log:
5/1/2017 10:35:27 AM Err PerformEmailActions->(AAMkADIwMWE2ODk2LTQ1NWItNDNlYy05ZmM0LTAxN2E2ZGY5OWUwZQBGAAAAAADUz+ZiheDPTIqj1zz/ixSXBwAawVP1PUYlRrm/FpoLPif7AAAAB0DUAACJv00WnRs5QaY78T8DdhPLAABYNw4EAAA=)->Saving email to: C:\temp\AAMkADIwMWE2ODk2LTQ1NWItNDNlYy05ZmM0LTAxN2E2ZGY5OWUwZQBGAAAAAADUz+ZiheDPTIqj1zz/ixSXBwAawVP1PUYlRrm/FpoLPif7AAAAB0DUAACJv00WnRs5QaY78T8DdhPLAABYNw4EAAA=\AAMkADIwMWE2ODk2LTQ1NWItNDNlYy05ZmM0LTAxN2E2ZGY5OWUwZQBGAAAAAADUz+ZiheDPTIqj1zz/ixSXBwAawVP1PUYlRrm/FpoLPif7AAAAB0DUAACJv00WnRs5QaY78T8DdhPLAABYNw4EAAA=.eml
5/1/2017 10:35:27 AM Err PerformEmailActions->(AAMkADIwMWE2ODk2LTQ1NWItNDNlYy05ZmM0LTAxN2E2ZGY5OWUwZQBGAAAAAADUz+ZiheDPTIqj1zz/ixSXBwAawVP1PUYlRrm/FpoLPif7AAAAB0DUAACJv00WnRs5QaY78T8DdhPLAABYNw4EAAA=)->Failed to save email, ex: The specified path, file name, or both are too long. The fully qualified file name must be less than 260 characters, and the directory name must be less than 248 characters.
5/1/2017 10:43:14 AM Debug ReceiveMail->PerformEmailActions on email with subject 'RE: [[IT_REQ #9101]] screen', index= 2 and UID= AAMkADIwMWE2ODk2LTQ1NWItNDNlYy05ZmM0LTAxN2E2ZGY5OWUwZQBGAAAAAADUz+ZiheDPTIqj1zz/ixSXBwAawVP1PUYlRrm/FpoLPif7AAAAB0DUAAAd29sQsZNMSaSMuIrx37SrAF9dWrQHAAA=
5/1/2017 10:43:14 AM Err PerformEmailActions->(AAMkADIwMWE2ODk2LTQ1NWItNDNlYy05ZmM0LTAxN2E2ZGY5OWUwZQBGAAAAAADUz+ZiheDPTIqj1zz/ixSXBwAawVP1PUYlRrm/FpoLPif7AAAAB0DUAAAd29sQsZNMSaSMuIrx37SrAF9dWrQHAAA=)->Saving email to: C:\temp\AAMkADIwMWE2ODk2LTQ1NWItNDNlYy05ZmM0LTAxN2E2ZGY5OWUwZQBGAAAAAADUz+ZiheDPTIqj1zz/ixSXBwAawVP1PUYlRrm/FpoLPif7AAAAB0DUAAAd29sQsZNMSaSMuIrx37SrAF9dWrQHAAA=.eml
5/1/2017 10:43:14 AM Err PerformEmailActions->(AAMkADIwMWE2ODk2LTQ1NWItNDNlYy05ZmM0LTAxN2E2ZGY5OWUwZQBGAAAAAADUz+ZiheDPTIqj1zz/ixSXBwAawVP1PUYlRrm/FpoLPif7AAAAB0DUAAAd29sQsZNMSaSMuIrx37SrAF9dWrQHAAA=)->Failed to save email, ex: Could not find a part of the path 'C:\temp\AAMkADIwMWE2ODk2LTQ1NWItNDNlYy05ZmM0LTAxN2E2ZGY5OWUwZQBGAAAAAADUz+ZiheDPTIqj1zz\ixSXBwAawVP1PUYlRrm\FpoLPif7AAAAB0DUAAAd29sQsZNMSaSMuIrx37SrAF9dWrQHAAA=.eml'.
5/1/2017 10:43:14 AM Debug ReceiveMail->TriggerEmail(AAMkADIwMWE2ODk2LTQ1NWItNDNlYy05ZmM0LTAxN2E2ZGY5OWUwZQBGAAAAAADUz+ZiheDPTIqj1zz/ixSXBwAawVP1PUYlRrm/FpoLPif7AAAAB0DUAAAd29sQsZNMSaSMuIrx37SrAF9dWrQHAAA=), hashcode: 9691421