SMTP authentication in postfix

hi,

I had configured smtp authentication in postfix mailserver.
the postfix version which am using is postfix 2.2
and for smtp authentication i use cyrus-sasl 2.1 version
And i had configured my client in MS outlook.
There was a option in MS Outlook that my outgoing(SMTP) server
requires authentication.
If i select this option in my outlook,and when i try to send mail from
any user
it is prompting for password.By giving the password i can able to send
mail.

But when i de-select the option in Outlook ie. my outgoing(SMTP)
server requires authentication.
its not asking for password so that any user can send mail to my
mailserver.

Could anyone plz say how to restrict the unknown sender to send mail,
or if any unknown sender
tries to send mail it must prompt for password.

This is my configuration paramters

[root@experts ~]# postconf -n
alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
broken_sasl_auth_clients = yes
command_directory = /usr/sbin
config_directory = /etc/postfix
daemon_directory = /usr/libexec/postfix
debug_peer_level = 2
fallback_relay = $mydomain
html_directory = no
inet_interfaces = all
mail_owner = postfix
mailbox_command = /usr/bin/procmail
mailq_path = /usr/bin/mailq.postfix
manpage_directory = /usr/share/man
mydestination = 151.2.119.150
mydomain = linux.com
myhostname = experts.linux.com
mynetworks = 151.2.0.0/16, 127.0.0.0/8
myorigin = $mydomain
newaliases_path = /usr/bin/newaliases.postfix
queue_directory = /var/spool/postfix
readme_directory = /usr/share/doc/postfix-2.2.10/README_FILES
relay_domains = $mydestination
sample_directory = /usr/share/doc/postfix-2.2.10/samples
sendmail_path = /usr/sbin/sendmail.postfix
setgid_group = postdrop
smtpd_sasl_auth_enable = yes
smtpd_sasl_local_domain = $myhostname
smtpd_sasl_security_options = noanonymous
unknown_local_recipient_reject_code = 550

Andhu wrote:
>
> But when i de-select the option in Outlook ie. my outgoing(SMTP)
> server requires authentication.
> its not asking for password so that any user can send mail to my
> mailserver.

I guess "any user within $my_networks" can send mail (not from
outside). If you really want to disable this, you'll have to
replace "permit_mynetworks" by "permit_sasl_authenticated"
(somewhere in main.cf, probably at "smtpd_recipient_restrictions".

-Matt