Let's say you don't want to run the Mailman mailing list manager. Since this is a default option in cPanel, there are several steps to completely disable it.
Note: new VPS's do not have Mailman enabled by default.

Disabling Mailman for cPanel Users

1. Log in to WHM

2. Navigate to Server Configuration and then Tweak Settings

3. Scroll down to Mail and uncheck the box for Mailman

4. Scroll to the bottom and click Save

Removing the Mailman Alias in Apache

1. Using SSH to connect to your server and login as root

2. Edit 'httpd.conf' (do not use the Virtuozzo file editor to do this) using vi or nano

   nano /usr/local/apache/conf/httpd.conf

    

3. Scroll down to these lines:

   Alias /mailman/archives/ /usr/local/cpanel/3rdparty/mailman/archives/public/
   ScriptAlias /mailman/ /usr/local/cpanel/3rdparty/mailman/cgi-bin/
   Alias /pipermail/ /usr/local/cpanel/3rdparty/mailman/archives/public/

4.  

   #Alias /mailman/archives/ /usr/local/cpanel/3rdparty/mailman/archives/public/

   #ScriptAlias /mailman/ /usr/local/cpanel/3rdparty/mailman/cgi-bin/

   #Alias /pipermail/ /usr/local/cpanel/3rdparty/mailman/archives/public/

    

   This disables the mailman aliases without removing the entry (you may want it later).

5. Save the file and restart Apache:

   service httpd restart

    

Removing the cron Entries

While logged in via SSH as root, enter this command:

crontab -d -i -u mailman

This will delete the mailman's nightly cron tasks. Alternately (recommended), you can edit mailman's crontab:

crontab -e -u mailman
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Comment out each line by placing a # in front of all the entries. Any line that already starts with a # is a comment.