[Mailman-Users] using hash for aliases. distribution email bounced back with errors

[Christian Stalberg]

Installing mailman 2.1.20 on a working postfix-dovecot-mysql mail server.
Trying to use hash for Mailman aliases.

In /etc/postfix/main.cf, I have

alias_maps = hash:/etc/aliases, hash:/var/lib/mailman/data/aliases

I ran 'newlist mailman at command line.' This is the aliases file contents. 

# This file is generated by Mailman, and is kept in sync with the
# binary hash file aliases.db.  YOU SHOULD NOT MANUALLY EDIT THIS FILE
# unless you know what you're doing, and can keep the two files properly
# in sync.  If you screw it up, you're on your own.

# The ultimate loop stopper address
mailman-loop: /var/lib/mailman/data/owner-bounces.mbox

# STANZA START: mailman
# CREATED: Fri Jun 14 13:09:26 2019
mailman:             "|/var/lib/mailman/mail/mailman post mailman"
mailman-admin:       "|/var/lib/mailman/mail/mailman admin mailman"
mailman-bounces:     "|/var/lib/mailman/mail/mailman bounces mailman"
mailman-confirm:     "|/var/lib/mailman/mail/mailman confirm mailman"
mailman-join:        "|/var/lib/mailman/mail/mailman join mailman"
mailman-leave:       "|/var/lib/mailman/mail/mailman leave mailman"
mailman-owner:       "|/var/lib/mailman/mail/mailman owner mailman"
mailman-request:     "|/var/lib/mailman/mail/mailman request mailman"
mailman-subscribe:   "|/var/lib/mailman/mail/mailman subscribe mailman"
mailman-unsubscribe: "|/var/lib/mailman/mail/mailman unsubscribe mailman"
# STANZA END: mailman

I ran bin/genaliases. I then subscribed some email addresses to the mailman
list and sent a test distribution email which was bounced back with errors
as follows:

This is the mail system at host naturalintelligence.us.

I'm sorry to have to inform you that your message could not be delivered to
one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can delete your own
text from the attached returned message.

                   The mail system

<mailman at naturalintelligence.us> (expanded from
    <mailman at lists.naturalintelligence.us>): host
    naturalintelligence.us[private/dovecot-lmtp] said: 550 5.1.1
    <mailman at naturalintelligence.us> User doesn't exist:
    mailman at naturalintelligence.us (in reply to RCPT TO command)

<post at naturalintelligence.us> (expanded from
    <mailman at lists.naturalintelligence.us>): host
    naturalintelligence.us[private/dovecot-lmtp] said: 550 5.1.1
    <post at naturalintelligence.us> User doesn't exist:
    post at naturalintelligence.us (in reply to RCPT TO command)

<|/var/lib/mailman/mail/mailman at naturalintelligence.us> (expanded from
    <mailman at lists.naturalintelligence.us>): host
    naturalintelligence.us[private/dovecot-lmtp] said: 550 5.1.1
    <|/var/lib/mailman/mail/mailman at naturalintelligence.us> User doesn't
exist:
    |/var/lib/mailman/mail/mailman at naturalintelligence.us (in reply to RCPT
TO
    command)


that have I done wrong please? thank you in advance.

Christian