thank you for your reply.
I tried the installation serveral times with different versions of SmarterMail (11,12,13), so I deleted the log folder again and again.
It was a strang situation, version 11 and 12 works fine, but every time when I updated to version 13 the site was runnig good on the WebServer which was delivered with SmarterMail on port 9998, but when I wanted to run the site on the IIS it fails.
My last try on Monday was to install version 13 with the MSI Installer and not with the Setup job and curiously now it works on the IIS too?
Di you have any idea why?