Hi

This does not sound like an issue with Firefox, but may be something that you will have to take up with the company concerned directly.

A company who keeps sending messages I don't want. On the site I can't find a button to stop sending the messages, so I want to block this company... Greets Anouke

Hi Anouke, are you talking about blocking email messages? If so, you should be using the settings in your email account -- not Firefox, (eg. gmail,yahoo mail, hot mail, aol mail, etc). In those settings, you can block someone.

Some e-mail providers have the option to sort incoming mail. Contact your e-mail provider for help.

Go here and register for protection for your e-mail and phones; https://www.donotcall.gov/ The National Do Not Call Registry