Mailman - set to hide 'from'

Hello, ok trying to setup a mailman list and want it so it hides the from and sets it the list email.

The docs say this can be done but not how?

http://staff.imsa.edu/~ckolar/mailman/mailman-administration-v2.html

Spam-specific posting filters

Hide the sender of a message, replacing it with the list address (Removes From, Sender and Reply-To fields)

can’t for the life of me work out how?

any ideas?

cheers