i wonder why they do it too.. at first i thought they might be using the account to send spam, as they have an MX record pointing there too.. but obviously this isnt possible just by pointing the record to our VPS.
Anyway, it does affect our search engine positions, or rather it has the potential to, which is why i wanted to sort it out. I work in web marketing and the site is one of my clients. I do not know the history of the french domain, what it is or has been used for, whether it is associated with spamming or not, or anything about it. The inclusion of it pointing to our website could have negative impacts on our own UK results. The fact that it is in france cause further potential problems.
Anyway, whether this is morally right or not, i've redirected the domain back to the company who it may be associated to. Ie..
xyzcompany.fr now redirects to xyzcompany.com (a real domain for a real company).
Ideally though, i'd want it gone.. my only other alternative is changing the IP of our site and see if the roguedomain follows it a few days later..
Its also strange that no one involved with the domain is replying to any emails i send.
Anyway,. thanks for the help.