Please follow the below steps to block the spam emails via cpanel.
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1. In the Mail section of the cPanel home screen, click Spam Assassin™.
2. On the SpamAssassin page, click Configure SpamAssassin.
3. In the required_score text box, type the number of hits required until a message is marked as spam.
4. In the score text boxes, you can assign scores to specific tests that SpamAssassin uses to examine incoming messages.
5. In the blacklist_from text boxes, you can specify e-mail addresses that are known spammers.
6. In the whitelist_from text boxes, you can specify e-mail addresses that are trusted, senders.
7. To save the new configuration, click Save.
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