When attempting to view mailman archive pages, or the administrative pages, you find a 500 error.
You may also find errors in the cPanel error log indicating that mailman cannot start:
[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.
This issue is most commonly caused by incorrect permissions on various Mailman files and directories.
You may resolve this by removing mailman from the RPM database and then force cPanel to re-install the RPM.
IMPORTANT: Please note that the following RPM command does not actually remove mailman. It only removes mailman from the RPM database. This makes it so that cPanel thinks that it is missing and needs to be installed. Deviating from these exact commands could cause damage to your server. Please use these exact commands and do not use any variation. Using the following commands does not pose any risk for data loss or other problems as long as they are used exactly as presented below.
1. Login to the server as the root user via SSH or Terminal
2. Issue the following commands:
rpm -e --justdb --nodeps cpanel-mailman
/usr/local/cpanel/scripts/check_cpanel_rpms --fix --targets=mailman