Section 8 - SMTP

Configure a system to forward all email to a central mail server

### Install and configure postfix and cyrus-sasl[root@rhel7server1 services]# yum install -y postfix cyrus-sasl cyrus-sasl-lib cyrus-sasl-plain [root@rhel7server1 services]# cd /etc/postfix
[root@rhel7server1 postfix]# vi main.cf
## use the following settingsqueue_directory = /var/spool/postfix command_directory = /usr/sbin daemon_directory = /usr/libexec/postfix data_directory = /var/lib/postfix mail_owner = postfix #inet_interfaces = localhost inet_protocols = all #mydestination = $myhostname, localhost.$mydomain, localhost unknown_local_recipient_reject_code = 550 alias_maps = hash:/etc/aliases alias_database = hash:/etc/aliases debug_peer_level = 2 debugger_command = PATH=/bin:/usr/bin:/usr/local/bin:/usr/X11R6/bin ddd $daemon_directory/$process_name $process_id & sleep 5 sendmail_path = /usr/sbin/sendmail.postfix newaliases_path = /usr/bin/newaliases.postfix mailq_path = /usr/bin/mailq.postfix setgid_group = postdrop html_directory = no manpage_directory = /usr/share/man sample_directory = /usr/share/doc/postfix-2.10.1/samples readme_directory = /usr/share/doc/postfix-2.10.1/README_FILESrelayhost = [smtp.gmail.com]:587 smtp_use_tls = yes smtp_sasl_auth_enable = yes smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd smtp_tls_CAfile = /etc/ssl/certs/ca-bundle.crt smtp_sasl_security_options=noanonymous smtp_sasl_tls_security_options=noanonymousinet_interfaces = loopback-only mynetworks = 127.0.0.0/8 [::1]/128 myorigin = $myhostname mydestination = local_transport = error: local delivery disabled ## Example, turning ON the "use of less secure protocol" (temporarily) for this demo !! Account -> Security ->## Change back to OFF after the test !!

## create sasl passwd file [root@rhel7server1 postfix]# vi sasl_passwd

/etc/postfix/sasl_passwd

[smtp.gmail.com]:587 your_id@gmail.com:your_password

## If not using gmail, but AWS SES as the relay host, replace similar to below. You must have a working AWS SES configured

/etc/postfix/main.cf ... relayhost = [email-smtp.ap-southeast-2.amazonaws.com]:587 ... /etc/postfix/sasl_passwd [email-smtp.ap-southeast-2.amazonaws.com]:587 <aws-ses-credential-username>:<aws-ses-credential-password>

## set owner and permission and create the hash for the sasl passwd file [root@rhel7server1 postfix]# postmap sasl_passwd [root@rhel7server1 postfix]# chown root:postfix sasl_passwd [root@rhel7server1 postfix]# chmod 640 sasl_passwd [root@rhel7server1 postfix]# postmap sasl_passwd ## enable and start postfix service [root@rhel7server1 postfix]# systemctl enable postfix [root@rhel7server1 postfix]# systemctl start postfix## send test email from the same machine## mail command line options : -r sets the from address, -s sets the subject [root@rhel7server1 ~]# mail -s "rhce objective - Configure a system to forward to a central mail server" webmaster@myfaqbase.com Hi webmaster Let me know if you can receive this email regards . EOT ## ALTERNATIVELY if the SMTP relay host has a restriction on the sender (from) email address, then [root@rhel7server1 ~]# mail -s "rhce objective - Configure a system to forward to a central mail server" -r allowedsender@somedomain.com webmaster@myfaqbase.com .... ## tail /var/log/maillog[root@rhel7server1 ~]# tail /var/log/maillog Jun 18 05:22:27 rhel7server1 postfix/pickup[11166]: 0050361511E6: uid=0 from=<root> Jun 18 05:22:27 rhel7server1 postfix/cleanup[11526]: 0050361511E6: message-id=<20200618092227.0050361511E6@rhel7server1.localdomain> Jun 18 05:22:27 rhel7server1 postfix/qmgr[11167]: 0050361511E6: from=<root@rhel7server1.localdomain>, size=592, nrcpt=1 (queue active) Jun 18 05:22:29 rhel7server1 postfix/smtp[11528]: 0050361511E6: to=<webmaster@myfaqbase.com>, relay=smtp.gmail.com[74.125.68.108]:587, delay=2.7, delays=0.17/0.14/1.5/0.91, dsn=2.0.0, status=sent (250 2.0.0 OK 1592472149 w22sm2334753pfq.193 - gsmtp) Jun 18 05:22:29 rhel7server1 postfix/qmgr[11167]: 0050361511E6: removed ## mail received

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