Software directory website, which I operate, received today email, asking to remove several records from the directory, which are software items of Somecompany. The email also stated that showing these items on my website is violation of copyright. The email was from email@example.com. Hovewer, there was no signature after text in the letter. And the man written the text did not introduce himself. The site of somecompany.com is closed. So, I have no idea, does this person has the rights to this software. This pops up in my mind the question, how can I check if this person is the owner of this software? What questions should I ask him? What type of evidence should he show me?