1.5. How do I turn off passwords completely?
Many people are uncomfortable with Mailman 2's monthly password reminders, because the passwords are sent in the clear. When you sign up for a new mailing list, you are notified that this will happen and you are encouraged to use a low-value password, but understandably, some people still do not want such monthly password reminders. In Mailman 3, passwords are both stored in hashed form (i.e. not clear text) and the monthly reminder feature has been removed.
In the meantime, monthly reminders can be disabled in Mailman 2.1 in three ways: by the user, by the list admin, and by the site admin.
A user may disable monthly reminders for a single list on a server, or for all lists on a server. To do this, go to your options page (yes, you will need your password to do this!) and scroll down to the section that says "Get password reminder email for this list?". Click on No and then Submit My Changes at the bottom of the page. If you want to disable password reminders for every mailing list you are subscribed to (with that email address) on the server, click the Set globally checkbox underneath the No button.
A list administrator may disable monthly password reminders for all members of their mailing list. To do this, log into your list's administrative page and go to General options. Scroll down to the field under Notifications that says Send monthly password reminders? Click on No and then on Submit Your Changes at the bottom of the page.
A site administrator may disable password reminders for all mailing lists on their system. To do this, remove the mailpasswds cron job.
Converted from the Mailman FAQ Wizard
This is one of many Frequently Asked Questions.