Spam is the name for unsolicited emails, that are often sent in large quantities. In this context unsolicited means that you have not given demonstrable and clear permission in advance for sending the email to your email address. In large quantities indicates that the message you received is part of a larger, identical transmission.
As of July 2009 sending spam is officially prohibited in the Netherlands. This is supervised by the Authority for Consumers & Markets (ACM), formerly known as OPTA. Complaints about spam can therefore be submitted to this organization. This spam prohibition applies to all European member states.
If you have spam complaints about a TransIP customer, you can contact us with the steps mentioned on the page linked here.