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--- linux_wiki:configure_a_system_to_forward_all_email_to_a_central_mail_server [2016/10/04 22:44]
billdozor [Forward Email: Postfix Setup]
+++ linux_wiki:configure_a_system_to_forward_all_email_to_a_central_mail_server [2019/05/25 23:50] (current)
@@ Line 11: / Line 11: @@
 ----
-====== Forward Email: Postfix Setup ======
+====== Lab Setup ======
-A mail null client forwards local email. It does not receive any mail from network sources.
+The following virtual machines will be used:
+  * server1.example.com (192.168.1.150) -> Configure SMTP null client (**on the exam**)
+  * server2.example.com (192.168.1.151) -> Configure central mail server for client testing (**NOT on the exam**)
+----
+====== Null Client Setup ======
+**THIS IS ON THE EXAM**: A mail null client forwards local email. It does not receive any mail from network sources.
+**From server1**.
 \\
@@ Line 29: / Line 39: @@
 \\
-Edit the main configuration
+Configure postfix parameters
-<code bash>
+  * Option A: Use postconf (faster if you have an idea what parameters you need to configure)<code bash># check a setting
-vim /etc/postfix/main.cf
+postconf relayhost
-## Set the origin (where mail came from) to the domain variable
+# check all settings
-myorigin = $mydomain
+postconf | grep <keyword>
+# configure - important
+postconf -e 'relayhost = [192.168.1.151]'
+# configure - probably already defaults (or set to localhost)
+postconf -e 'inet_interfaces = loopback-only'
+postconf -e 'mydestination ='
+postconf -e 'mydomain = example.com'
+</code>
+  * Option B: Edit the main configuration<code bash>vim /etc/postfix/main.cf
 # Relayhost to forward mail to
-# gmail for testing purposes; exam will provide an IP/hostname of a mail server to use
+relayhost = [192.168.1.151]
-relayhost = [smtp.gmail.com]:587
-# Forward from loopback interfaces and networks only (local system)
+# Forward from loopback interfaces
 inet_interfaces = loopback-only
-mynetworks = 127.0.0.0/8 [::1]/128
 # Configure destination as blank, because we aren't delivering mail locally (only forwarding outgoing)
 mydestination =
-# Prevent postfix from putting mail into mail boxes
+# Configure domain
-local_transport = error: local delivery disabled
+mydomain = example.com
 </code>
 \\
-**NOT ON EXAM** -> Gmail specific: Add gmail settings to the main.cf file
+Check postfix syntax
 <code bash>
-vim /etc/postfix/main.cf
+postfix check
+</code>
+\\
-#### Gmail specific settings - NOT ON THE EXAM ####
+Restart the service
-smtp_use_tls = yes
+<code bash>
-smtp_sasl_auth_enable = yes
+systemctl restart postfix
-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 = noanonymous
-#### End of Gmail specific settings ####
 </code>
+----
+====== Postfix Central Mail Server ======
+**THIS IS NOT ON THE EXAM**: This section setups up a mail server to receive mail in order to test the null client configured previously.
+**From server2**
 \\
-**NOT ON EXAM** -> Gmail specific: Config to sign into a secure SMTP
+Install postfix
 <code bash>
-vim /etc/postfix/sasl_passwd
+yum install postfix
+</code>
-[smtp.gmail.com]:587 username@gmail.com:password
+\\
+Enable and start postfix
+<code bash>
+systemctl enable postfix
+systemctl start postfix
 </code>
-  * Replace username and password with actual gmail username and password.
 \\
-**NOT ON EXAM** -> Gmail specific: Set restrictive permissions on the sasl file
+Open the firewall to receive SMTP
 <code bash>
-chown root:postfix /etc/postfix/sasl_passwd
+firewall-cmd --permanent --add-service=smtp
-chmod 640 /etc/postfix/sasl_passwd
+firewall-cmd --reload
 </code>
 \\
-**NOT ON EXAM** -> Gmail specific: Convert sasl file so postfix can use it
+Edit the main configuration file
 <code bash>
-postmap /etc/postfix/sasl_passwd
+#-- vim directly
+vim /etc/postfix/main.cf
+# listening interfaces
+inet_interfaces = all
+# Accept mail for these domains
+mydestination = example.com, server2.example.com, server2
+#-- postconf method
+# check settings
+postconf | grep inet_
+postconf | grep mydestination
+# configure
+postconf -e 'inet_interfaces = all'
+postconf -e 'mydestination = example.com, server2.example.com, server2'
 </code>
@@ Line 93: / Line 137: @@
 <code bash>
 postfix check
+</code>
+\\
+Restart the service
+<code bash>
+systemctl restart postfix
 </code>
 ----
-====== Forward Mail: Client Mail Testing ======
+====== Null Client Testing ======
+**From server1**
 Install a mail client (if not already installed)
@@ Line 107: / Line 159: @@
 Send a test message
 <code bash>
-echo "This is the subject body" | mail -s "This is a postfix forward test" username@gmail.com
+echo "Did it work?" | mail -s "This is a postfix forward test" root@server2.example.com
 </code>
@@ Line 114: / Line 166: @@
 <code bash>
 tail -f /var/log/maillog
+</code>
+\\
+**From server2**
+On the postfix relayhost, check root's mail
+<code bash>
+mail
+</code>
+----
+====== Troubleshooting ======
+On the sending client, to view the mail queue
+<code bash>
+postqueue -p
+</code>
+\\
+Flush the sending mail queue after fixing a problem to get rid of stuck messages
+<code bash>
+postqueue -f
+</code>
+\\
+If a message is stuck and won't flush, it can be removed
+<code bash>
+postsuper -d <queue_id>
+</code>
+  * Instead of a single queue_id, you can specify the keyword 'ALL'
+\\
+On the receiving server, check the maillog for reasons a message did not deliver
+<code bash>
+tail /var/log/maillog
 </code>
 ----