Why rsyslog is not able to collect any system logs since upgrade to RHEL8 ?

Issue

• The mail logs are not collected in /var/log/maillog but collected in journal logs.
  • The mail activity is showing up in output of systemctl status postfix. I would expect it to show up in /var/log/maillog as well.
• The logs related to mails/postfix are collected by systemd-journald in journal logs but are missing or not collected in /var/log/maillog.
• Why rsyslog is not able to collect any system logs ?