Plesk 8.6 gives 301 redirect on every domain

[JeroenV]

Recently we discovered our website has been removed from Google, due to so called empty redirects. After 2 days of testing and checking we discovered this is because our website, running on Plesk, returns a "301 Moved Permanently" when requesting a page on HTTP/1.0 without Host-headers.

Since this same problem occurs for almost every one of our clients, we figured this would be some kind of Plesk error. Also, some of our clients domains return the default Plesk page when requesting a page with HTTP/1.0 without Host-headers.

Examples:
http://web-sniffer.net/?url=http://www.hcdesigns.nl/&gzip=yes&http=1.0 (our own domain)
http://web-sniffer.net/?url=http://www.mercatorpayments.nl/&gzip=yes&http=1.0 (a client giving default Plesk page)
http://web-sniffer.net/?url=http://www.tic.nl/&gzip=yes&http=1.0 (a client getting a 301)

More info:
Plesk Panel 8.6 on Debian Etch