QUOTE(nic800 @ Feb 13 2009, 10:26 AM)

I repeated the setup process once again. There is no error. I get a "success... Thank you for registering your mailhost with spamcop" reply.
OK, thanks for that.
QUOTE
But as soon as I try to report spam, the same error message appears again.
Back to the example mentioned above..
The "supposed receiving system" is 212.223.168.71, right?
That is in fact the IP address that is listed under "Relaying IPs" in my mailhost configuration.
You probably will want to follow the next set of words I offered above. However, my questions would start with a description of just how you are 'getting' this e-mail. I find the headers and your exampled words a bit confusing.
"Relaying IPs" suggests something not quite expected in normal conversation about your specifying an actual Host, but perhaps others that use the MailHost Configuration will jump in, perhaps telling me that this is normal ...???
I'm not sure I understand the headers at all, actually .... the first line seems to be a bit of crap (but then again, this might have something to do with just how you're collecting your e-mail .. I've looked at several "received by/from Google and I can't see anything similar at all.)
The second Received: line is just odd .... whereas the first line includes a FQDN (Fully Qualified Domain name) for the receiving system, the second Received line does not .... "
MAILCENTRAL7" should really read as "
mailcentral7.internet1.de" ... and the rest of the construct of that line seems a bit out of kilter.
This may be something that Don/Deputies might be able to work around in their hands-on massaging of the MailHost Configuration database, but that's not for me to say.