Yes, you can modifie your default configuration for reply to the list, and no to sender.
Download my mod file from here
http://www.todomecanica.com.ar/ezmlmrcand replace the current file located at /etc/ezmlm/ directory.
All these modification are documented perfectly in ezmlm page.
If you want, compare the files to see the diferences.
These new settings are aplyed when you create a new list. In your case, delete all your list. Download and replase the above file, and then recreate the lists.
If you want back up the existing users, backup the folder /home/e-smith/files/ezmlm/lists/listname/subscriber/.
Then, when you finished create the list, put your subscribers backup folder into each list.
Enjoy
Tips. This conf file increase attachemnt size, reply to the list.
If you want the users send html messages, and any type of attachements, go to the configuration of the list and delete all content under "Mime types to strip from all outgoing mail" title.