Most websites provide a general contact email for users to get in touch with. This would usually be in the “Contact” tab or in the imprint. Although the person you are trying to reach may not be the one to answer your query, you could ask for the correct email address. This way you can be sure that your email reaches the intended addressee.
Alternatively, many websites provide the option of subscribing to a mailing list. When you reply to a newsletter, you have a direct personal contact within the company, making it easier to find the email address you are looking for. Unfortunately, this does not work with all newsletters. Some prevent replies.