Problem with error 404 hacking.

[Krenshau]

I created custom error 404 and 500 pages that send me an email when there is a problem. I did this so if there was a dead link or something, I would be notified. Howerver, I am having a big problem I don't know how to fix. I am getting tons of email (over 300 this morning), but here is what I don't understand. I collect the referrer page, and the page that is being requested, for my email. The problem is, the referrer and the requested page are not my domain!?!?! How can this be possible? More importantly, how can I stop this?

If I had to guess, I would think that someone is using my error pages, but is that possible? I have included an example below. One other bit of information; the domains are not from the same site, there are many different domains that are coming in my email. Any help with this would be really great.

There has been an error:
The user was coming from page: [url]http://www.jobsandjobs.de/[/url]
The user was going to: [url]http://www.jobsandjobs.de/error404.aspx?404;http://www.jobsandjobs.de:80/eintragism_premium.php[/url]
Error occured on:
12/2/2006 10:26:55 AM
The user's IP is: 59.120.55.183

Thank you for your help.

Edit: BTW, this is ASP .NET 2.0. Just incase that matters.

Edit 2: One other thing I just noticed. On the last batch that I got today. The IP address is the same on all of them. I am not sure what that means, though.