Getting tons of Excessive resource usage emails

Occasionally I get alerts of "Excessive resource usage". Time: Sat Dec 7 14:50:22 2019 +0800 Account: reconvaluecom Resource: Process Time Exceeded: 35705 > 1800 (seconds) Executable: /usr/local/cpanel/3rdparty/perl/528/bin/perl Command Line: spamd child PID: 32045 (Parent PID:30638) Killed: No Everyday I received email that same user trying to sneak in via dovecot: imap-login using different IP address after the lfd blocked the IP. Also got suspicious process running on my server. This has made my server have very high bandwidth usage. Is there any way to prevent this from happening?