I've received a letter like this after each show I have done. The first time, I didn't realise that it was a scam until almost too late, so this time I thought I'd make sure no one falls into that trap.
At first glance it looks like a letter from Top Drawer - the trade show I recently attended, but if you look closely, there is a very pale logo behind showing the real origin - a company based based in Mexico called Expo Guide. Attached is a form asking for up to date contact details. A fairly routine occurrence, and you might just absentmindedly fill it in and post it back.
I've circled the really sneaky bits in red. There is no affiliation to the event, and filling out the form actually means you're signing up for a three year listing priced at 1271 Euros a year, or whatever they choose to call the equivalent in Mexican Pesos.
DON'T DO IT!!
Burn it or rip it up, or report it, but please don't fill it in (unless you think it sounds like a good deal!?)
One of the images below shows the actual terms and conditions printed so palely that they are almost indecipherable. I've edited the image to make them possible to read. In my case, the letters have been sent after Top Drawer (this is what they have to say on the matter), but I expect that they probably target attendees of any trade shows. It only takes a handful of people to fill them out and then feel sufficiently threatened by the subsequent inevitable debt collecting letters to make it worth their while.
Please share this with anyone you think might be a target, and hopefully one day they might cease to exist.