Can not unsubscribe or block their e-mails

This company regularly send me and the rest of my colleagues promotional e-mails. The "unsubscribe" button at the bottom of the e-mail have no effect and it is also impossible to block their e-mails. They also do not respond to a e-mail from my side requesting them to remove me from their distribution list. Unfortunately they are just one of many companies that have this pestering attitude. Because of this I will NEVER make use of any of their services - just out of principle. So marketing people...you achieve the opposite of what you were hoping for.