Error in configuration file /etc/dovecot/conf.d/98-sieve.conf line 24: Unknown section name: plugin

Symptoms

• Plesk Obsidian was upgraded to 18.0.73;
• Dovecot was upgraded to 2.4.1;

• Dovecot fails to start with error:

  CONFIG_TEXT: Oct 16 07:15:06 www dovecot[33856]: doveconf: Fatal: Error in configuration file /etc/dovecot/conf.d/98-sieve.conf line 24: Unknown section name: plugin

Cause

This behavior occurs due to the recent update to Dovecot version 2.4.1. and this file uses the deprecated plugin section:
Upgrading Dovecot CE from 2.3 to 2.4

Resolution

1. Connect to the Plesk server via SSH.

2. Remove plugin section in /etc/dovecot/conf.d/98-sieve.conf;

   # cat /etc/dovecot/conf.d/98-sieve.conf
   sieve_max_redirects = 10