Here are some of the best practices that you can follow to avoid email abuse on your cPanel server.
# Password Strength Configuration :
If you increase the password strength, you can decrease the chance that a hacker will correctly guess passwords.
WHM >> Home >> Security Center >> Password Strength Configuration
# Enable cPHullk
If you enable cPHulk, you can decrease the chance that a hacker can use a brute force attack on your server.
WHM >> Home >> Security Center >> cPHulk Brute Force Protection
# SMTP restrictions
If you enable the SMTP Restrictions feature, spammers cannot directly interact with remote mail servers or work around mail security settings.
WHM >> Home >> Security Center >> SMTP Restrictions
# Max hourly emails per domain
This setting specifies the maximum number of emails that each domain can send per hour.
WHM >> Home >> Server Configuration >> Tweak Settings
# Prevent “nobody” from sending mail
WHM >> Home >> Server Configuration >> Tweak Settings