Trademark Infringement Investigation

I received an email with the subject "Trademark Infringement Investigation" last night. At first I was just about to bin it - I don't ever remember receiving a digitally signed email before and thought it was spam!

I eventually clicked on the 'continue' button and read the email. One part states 'This notice is being sent to you as a courtesy to inform you that a fraudulent business impersonator may have involved you in the unlawful act of Trademark infringement, as we feel you may be unaware that the use of our Trademark and Trade-names was not authorized.'

Erm, what? It continues: 'Please, remove any and all of our Trademarks and/or Trade-names, which are the exclusive property of Emerald Passport, Inc., from every web property (e.g. websites, PPC ads, link exchange, etc.) that you own and/or operate and kindly provide us with information as to how you came to use our Trademark as a link advertisement on your website (e.g. copy of a request to partner with you using our Trademark/Trade-names, name of link exchange provider, method by which you were contacted: email, telephone call, etc.)'. So what dreadful act had I taken part in to infringe the trademark of this company (if, indeed, it is infringement - I'm no legal expert)?

I'd accepted a link exchange! The link was probably accepted when I first set up the site - in early 2006. Maybe even before that. And they are demanding that I tell them where I got the link exchange from. I think that would be fairly obvious - the affiliate or reseller that I was linking to.

My question quite simply is - is sending threatening legal demands via email the most efficient way of dealing with this problem? Surely it would be more efficient to tell their affiliates / resellers to sort their act in the first place. I suppose that if some have arranged hundreds, or thousands, of link exchanges, some might not have the documentation to follow up and request the changes. But why ask me to potentially break the Data Protection Act and pass my exchange's contact details? If it's a link to their affiliate's site - do they not know who the affiliate was?

I looked on the link exchange directory and there were at least another 3 or 4 sites using similar anchor text, so they must have quite a task on their hands. I was just amazed they found the page - what search engine actually has that ancient page cached?