Postfix

alias_maps = hash:/etc/aliases
config_directory = /etc/postfix
local_only = check_recipient_access hash:/etc/postfix/local_domains, reject
smtpd_recipient_restrictions = check_sender_access hash:/etc/postfix/restricted_senders, check_relay_domains hash:/etc/postfix/relay_domains, reject_unauth_destination, defer_if_permit
smtpd_restriction_classes = local_only
virtual_alias_maps = pcre:/etc/postfix/virtual

error log:

Apr 20 23:48:41 box2 postfix/smtpd[1914]: connect from unknown[10.0.3.33]
Apr 20 23:48:41 box2 postfix/smtpd[1914]: NOQUEUE: reject: RCPT from unknown[10.0.3.33]: 554 5.7.1
<foo@bar.org>: Sender address rejected: Access denied; from=<foo@bar.org> to=<01tonythomas@gmail.com> proto=ESMTP helo=<localhost>
Apr 20 23:48:41 box2 postfix/smtpd[1914]: disconnect from unknown[10.0.3.33]