Please check configuration settings of Mailman server extensions. Better install Mailman with proper configuration details as shown below.....
To install Mailman, connect to your virtual server via SSH or telnet. Mailman requires Python 2. If you have not installed it, install python2, then use the appropriate commands for your virtual server operating system.
% vinstall mailman
The rehash command relinks the wrapper scripts, such as the newlist command, and links any new commands that may have been installed. If you want to change your administrative password, use the mmsitepass command.
% mmsitepass NEW-PASSWORD
To start the Mailman daemon, run the following command (you may want to include this command in your ~/etc/rc file to start Mailman whenever the server reboots):
Mailman uses a number of cron commands to manage the mailing lists. These are loaded into your crontab by default when Mailman is installed. If you have other cronjobs, you may want to insert the Mailman cronjobs into your custom cron file. To do this, copy the lines from the Mailman cronfile into your custom cronfile, then load that file into cron. You can find the Mailman cronfile in the following file on your virtual server.