Hi,
When I translate the error with google translate, it says "It could not be contacted because the destination computer refused to connect", so the smtp server refused the connection. Maybe it only allows connections from specific hosts, or maybe the configuration is not correct. Also, many ISPs (like most cable companies in the US, Comcast, Time Warner for example) block port 25 to prevent spam on their networks so often you can't relay from a local test machine to an smtp server on the internet using port 25. I can't on my dev machine. Thats why many email services like yahoo and google use alternate ports like 587 these days for smtp. I don't know if they do that in Germany but thought its worth mentioning in case they do.
I can tell you that the settings used by the Create User Wizard and the Password Recovery and Registration Email confirmation is all using these settings:
<system.net>
<mailSettings>
<smtp from="andreas@klaeser-andreas.de">
<network
host="smtp.klaeser-holzbearbeitung.de "
port="25"
password="MyPassword"
userName="MyUserName"
/>
</smtp>
</mailSettings>
</system.net>
The other settings in the appSettings section are used by the contact form, blog comment notification, forumpost notification, etc.
Hope it helps,
Joe