If you periodically receive spam or other undesired mails from a certain sender or domain, you can add the sender to your blacklist. Emails from senders on the blacklist will always be categorized as spam, even if the emails would otherwise have passed the spam check.
To manage the blacklist, follow these steps:
In the spam filter configuration, select the desired email address and select «Configuring whitelists and blacklists».
Enter the email address or domain in the text field under «Blacklist» if you would like the spam filter to categorize all emails from this address/sender as spam.
You can enter a specific email address (e.g. «sender@domain.ending») or «*@domain.ending» to block the entire domain.
Click «Add» to confirm your entry.