I am trying to configure mailman with zimbra using the following URL

According to the doc, need to modify /opt/zimbra/postfix/conf/main.cf as
virtual_alias_maps = ldap:/opt/zimbra/conf/ldap-am.cf,hash:/usr/local/mailman/data/virtual-mailman
alias_maps = hash:/etc/aliases,hash:/usr/local/mailman/data/aliases

But main.cf(i.e postfix configuration) is resetting to its orginal(or regenerating a file) when posfix is restarted.

Can you pl. help us to resolve the problem.

Thanks in advance.

- Dayakar