500 Error on Mailman Archive and Admin Pages

Symptoms

When attempting to view the Mailman archive pages or the administrative pages, you receive a 500 error, and an error similar to the following may be found in the cPanel error log.

[2021-03-11 13:28:06 +0530] info [startmailman] systemd failed to start the service “mailman” (The “/usr/bin/systemctl restart mailman.service --no-ask-password” command (process 15734) reported error num
ber 1 when it ended.): Job for mailman.service canceled.

Description 

Incorrect permissions on various Mailman files and directories most commonly cause this issue. Removing the cpanel-mailman package from the RPM database and then reinstalling the package will correct the permissions.

Resolution

1. Access the server's command line as the 'root' user via SSH or "Terminal" in WHM.
2. Remove the cpanel-mailman package.
   • RHEL-based systems

     rpm -e --justdb --nodeps cpanel-mailman

     Please note that the RPM command does not actually remove the cpanel-mailman package; it only removes the package from the RPM database.
   • Ubuntu

     apt remove cpanel-mailman -y

3. Reinstall the cpanel-mailman package.

   /usr/local/cpanel/scripts/check_cpanel_pkgs --fix --targets=mailman