Restricting users to send mails to off-site destinations in Postfix & Zimbra

Hi...

Configuring Postfix in a way that some users can only send mails to internet and some users not. The users without internet access should get bounce message.

This steps can also use in zimbra

/etc/postfix/main.cf:
 smtpd_recipient_restrictions = check_sender_access hash:/etc/postfix/restricted_senders
     ...other stuff...

 smtpd_restriction_classes = local_only
 local_only =
     check_recipient_access hash:/etc/postfix/local_domains, reject

/etc/postfix/restricted_senders:
 foo@domain      local_only
 bar@domain      local_only

/etc/postfix/local_domains:
 this.domain     OK      matches this.domain and subdomains
 that.domain     OK      matches that.domain and subdomains

Once after adding email id restricted_senders, the database should get updated.

Run following commands :
/opt/zimbra/postfix/sbin/postmap:~ /opt/zimbra/postfix/conf/restricted_senders

/opt/zimbra/postfix/sbin/postfix reload