How to disable SMTP auth in iredmail?

==== Required information ====
- iRedMail version: iRedMail-0.8.4
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): LDAP
- Linux/BSD distribution name and version: kubuntu 12.04
- Related log if you're reporting an issue: ----------
====

I have installed iredmail for developing purpose and it works fine (many thanks in advance!)
But now i want to disable SMTP Authentication (Not SSL or TLS)for developing purpose too!
How can i do that?