Here is a snip from my log file earlier today:
Feb 3 13:54:24 efa postfix/smtpd[2235]: NOQUEUE: reject: RCPT from unknown[74.117.133.204]: 554 5.7.1 <
bcarter@argos.k12.in.us>: Relay access denied; from=<
Frank_C@wauffnursy.com> to=<
bcarter@argos.k12.in.us> proto=ESMTP helo=<jhpu204.wauffnursy.com>
Feb 3 13:54:27 efa postfix/smtpd[2235]: NOQUEUE: reject: RCPT from unknown[74.117.133.204]: 554 5.7.1 <
vharley@argos.k12.in.us>: Relay access denied; from=<
Frank_C@wauffnursy.com> to=<
vharley@argos.k12.in.us> proto=ESMTP helo=<jhpu204.wauffnursy.com>
Feb 3 13:54:29 efa postfix/smtpd[2235]: NOQUEUE: reject: RCPT from unknown[74.117.133.204]: 554 5.7.1 <
bbarrett@argos.k12.in.us>: Relay access denied; from=<
Frank_C@wauffnursy.com> to=<
bbarrett@argos.k12.in.us> proto=ESMTP helo=<jhpu204.wauffnursy.com>
Feb 3 13:54:55 efa postfix/smtpd[2235]: NOQUEUE: reject: RCPT from lcmail.doe.in.gov[165.139.1.50]: 554 5.7.1 <
swilliams@argos.k12.in.us>: Relay access denied; from=<
noreply@doe.in.gov> to=<
swilliams@argos.k12.in.us> proto=ESMTP helo=<lcmail.doe.in.gov>
Feb 3 13:56:22 efa postfix/smtpd[2235]: NOQUEUE: reject: RCPT from send1.mmsend22.com[209.18.93.56]: 554 5.7.1 <
jspencer@argos.k12.in.us>: Relay access denied; from=<
NSTA@mmsend53.com> to=<
jspencer@argos.k12.in.us> proto=ESMTP helo=<send1.mmsend22.com>
Feb 3 13:58:41 efa postfix/smtpd[2276]: NOQUEUE: reject: RCPT from lcmail.doe.in.gov[165.139.1.50]: 554 5.7.1 <
nmedich@argos.k12.in.us>: Relay access denied; from=<
noreply@doe.in.gov> to=<
nmedich@argos.k12.in.us> proto=ESMTP helo=<lcmail.doe.in.gov>
Feb 3 13:59:26 efa postfix/smtpd[2276]: NOQUEUE: reject: RCPT from na3sys009aog106.obsmtp.com[74.125.149.77]: 554 5.7.1 <
nmedich@argos.k12.in.us>: Relay access denied; from=<
cfansler@jgsc.k12.in.us> to=<
nmedich@argos.k12.in.us> proto=SMTP helo=<na3sys009aog106.obsmtp.com>
Feb 3 13:59:37 efa postfix/smtpd[2276]: NOQUEUE: reject: RCPT from mta.e.thirtyonegifts.com[199.122.123.78]: 554 5.7.1 <
jstults@argos.k12.in.us>: Relay access denied; from=<
bounce-903_HTML-54095488-372910-7001724-3810@bounce.e.thirtyonegifts.com> to=<
jstults@argos.k12.in.us> proto=ESMTP helo=<mta.e.thirtyonegifts.com>
Feb 3 13:59:50 efa postfix/smtpd[2276]: NOQUEUE: reject: RCPT from zimbra.niesc.k12.in.us[165.138.207.23]: 554 5.7.1 <
leep75@argos.k12.in.us>: Relay access denied; from=<
lturner@niesc.k12.in.us> to=<
leep75@argos.k12.in.us> proto=ESMTP helo=<zimbra.niesc.k12.in.us>
Feb 3 14:00:34 efa postfix/smtpd[2276]: NOQUEUE: reject: RCPT from zimbra.jesse.k12.in.us[165.138.207.20]: 554 5.7.1 <
tsabanski@argos.k12.in.us>: Relay access denied; from=<
jramer@jesse.k12.in.us> to=<
tsabanski@argos.k12.in.us> proto=ESMTP helo=<zimbra.jesse.k12.in.us>
Feb 3 14:05:24 efa postfix/smtpd[2381]: NOQUEUE: reject: RCPT from ccm180.constantcontact.com[208.75.123.180]: 554 5.7.1 <
eendres@argos.k12.in.us>: Relay access denied; from=<AuJotonXFTDKl5A2KlTvM0g==_1111906731166_b4IzwHhEEeO+m9SuUnU2zg==@in.constantcontact.com> to=<
eendres@argos.k12.in.us> proto=ESMTP helo=<ccm180.constantcontact.com>
Feb 3 14:06:03 efa postfix/smtpd[2381]: NOQUEUE: reject: RCPT from lcmail.doe.in.gov[165.139.1.50]: 554 5.7.1 <
swilliams@argos.k12.in.us>: Relay access denied; from=<
noreply@doe.in.gov> to=<
swilliams@argos.k12.in.us> proto=ESMTP helo=<lcmail.doe.in.gov>
Feb 3 14:08:41 efa postfix/smtpd[2423]: NOQUEUE: reject: RCPT from lcmail.doe.in.gov[165.139.1.50]: 554 5.7.1 <
jdelp@argos.k12.in.us>: Relay access denied; from=<
noreply@doe.in.gov> to=<
jdelp@argos.k12.in.us> proto=ESMTP helo=<lcmail.doe.in.gov>