How do I delete unwanted chat pop-ups from strangers.?

[gloria]

Dear Yahoo Representative,
It is extremely annoying to have to respond often to chat pop-ups every time I access my email messages. Although you gives us the option to block chat pop-ups from people we know, you don't give us the option to bock chat pop-ups from people we don't know. For all I know, a murders may be trying to contact me. My question to you is how can I continue using your email services without having to keep responding to chat pop-ups? If you don't have a solution for me that can address this problem, please let me know as soon as possible so that I can move on to another email service provider. Gloria