Hi Nicolas,
When you upgraded to SmarterMail 13, did you uninstall the previous version first, or did you install version 13 on top of an existing version?
If you installed on top, please perform a reinstallation following these steps:
1. Stop the SmarterMail application pool in IIS.
2. Uninstall SmarterMail from the Control Panel
3. Rename C:\Program Files (x86)\SmarterTools\SmarterMail to SmarterMail_OLD
4. Download and install SmarterMail from here.
5. Stop the SmarterMail service.
6. Transfer the following files from the SmarterMail_OLD folder to the same location in the newly created SmarterMail folder:
--- All XML files located \SmarterMail_OLD\Service\
7. Start the SmarterMail service.
8. Start the SmarterMail application pool in IIS.