Hi Jens.
Try to uninstall the actual MSMAPI32.DLL file, download the new dll file for Windows 10 and register the new file in Windows.
*Before unregister the dll, download the new dll file for windows 10.
Follow the steps:
1- Open the execute in windows (Window + R command)
2- Execute the command "regsvr32 -u C:\Program Files (x86)\Common Files\SYSTEM\MSMAPI\1040\MSMAPI32.DLL"
3- Download the MSMAPI32.DLL for Windows 10 (link for example: http://fix4dll.com/mapi32_dll)
4- Register the new dll in Windows using the command "regsvr32 <file location>\MSMAPI32.DLL"
I hope it works.
Best regards
Ricardo Pereira