“amavisd.service failed” error when installing Plesk Email Security extension

I was trying to install Plesk Email Security in my Plesk server, but an error popped up because amavisd.service failed to start. The error was exactly quoted like this:

Execution systemctl has failed with exit code 1, stdout: , stderr: Job for amavisd.service failed because the control process exited with error code. See "systemctl status amavisd.service" and "journalctl -xeu amavisd.service" for details.

You can directly use amavisd to verify what caused the error: /usr/sbin/amavisd -c /etc/amavisd/amavisd.conf 2>&1

If the debug shows something about missing additional required dependencies (here, modules), like:

ERROR: MISSING REQUIRED ADDITIONAL MODULES:
  DBD::mysql
  DBD::mysql

Then DBD::mysql Perl module is missing. Simple fix:

# Install
sudo dnf install perl-DBD-MySQL -y

# Then start amavisd.
sudo systemctl start amavisd

# Verify if amavisd started or not.
sudo systemctl status amavisd

If it starts cleanly, go back to Plesk and retry installing the email security extension.