Mailman not integrating with postfix properly

Question

I installed postfix on my local machine and able to send mails to local users i.e. shivams in my case which is username of the account. Also i am able to send mail outside of my machine for ex. gmail.com etc. It is other thing that they are marking those mails as spam but things are working.

I installed mailman for managing mailing lists. It is working fine. I am able to open web interface properly. Able to look at archives. Also able to make new mailing lists from web interface and from terminal. If i subscribe someone to a mailing list then that account is getting email regarding subscription. This shows that mailman is working properly and is able to use postfix to send emails.

To send emails to mailing lists i add these lines to /etc/postfix/main.cf file. I used postconf for it.

relay_domains = lists.example.org
mailman_destination_recipient_limit = 1 
transport_maps = hash:/etc/postfix/transport

My hostname is lists.example.org.

Entry in /etc/postfix/transport file is

lists.example.org mailman:

Also in my /etc/alias this is the entry

# /etc/aliases
mailer-daemon: postmaster
postmaster: root
nobody: root
hostmaster: root
usenet: root
news: root
webmaster: root
www: root
ftp: root
abuse: root
noc: root
security: root

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" 

Now if i try to send mail to mailman@lists.example.org using mutt then i get this error. Also all mails stopped to go with same error. But as soon i remove those three lines from main.cf mails to local user and to email account on internet start to work.

7161E121843      439 Fri Jun 12 01:24:06  shivams@lists.example.org
                                                (address resolver failure)
                                     mailman@lists.example.org

I am not able to understand why i am not able to send emails to mailing list from mutt. Ideally this should be working and this is the way i found on web to integrate mailman with postfix. Please suggest if i am missing something because individually both are working but together they seem to hate each other.

Answer 1

This is going to be an incomplete answer but I hope it gets you on track. The transport you specified in your transport table has to point to something Postfix knows about (and a transport has nothing to do with your aliases). That is, "mailman" needs to be defined in master.cf. Most postfix installations come with an example mailman service in master.cf commented out, which is probably a good place to start.