Spam email but I can not block the domain

Spam email but I can not block the domain

Hi,

We are using zoho mail for years. I get spam emails recently from certain domain, but sender address is wrong. I can not block the sender

Please check the screenshot. Sender and recipient is: office@kosser
I have add the domain "kosser.net" to blacklist but not blocked yet.
spam

please advise
BR
Emre