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 firstname.lastname@example.org. 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?
If you are violating a copyright and you know it, then that is a problem to begin with. If you are using what you are using legitimately, then they should have a certificate of registration to prove that they own the rights to the software.
Hard to see how having items in a directory would violate copyright. Might violate trademarks, though that can be resolved easily enough by using the appropriate trademark mark and a bit of blurb saying who the trademark belongs to.