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Config postfix smarthost » Historie » Version 1

Jeremias Keihsler, 13.01.2017 12:07

1 1 Jeremias Keihsler
h1. Setting up Postfix to send mails via external mail-account
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h2. Preliminary note
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See also:
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* https://www.zulius.com/how-to/set-up-postfix-with-a-remote-smtp-relay-host/
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* http://rs20.mine.nu/w/2011/07/gmail-as-relay-host-in-postfix/
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A typical email scenario: you're a developer, and you've got a development Linux box at home. You need to be able to send emails from your code or cron jobs, but you're too lazy to set up a full fledged email server on your LAN. Or you just want to use an email account provided by Google Apps, Yahoo, your ISP or in our case a iRedMail-installation.
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h2. Install postfix
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Should be preinstalled, as it is the default mail-handler with CentOS
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<pre><code class="bash">
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yum install postfix cyrus-sasl cyrus-sasl-gssapi cyrus-sasl-plain
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</code></pre>
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h2. configure postfix
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<pre><code class="bash">
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vim /etc/postfix/main.cf
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</code></pre>
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<pre>
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myorigin = example.com
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# Set this to your email provider's smtp server.
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# A lot of ISP's (ie. Cox) block the default port 25
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# for home users to prevent spamming.  So we'll use port 80
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relayhost = mail.example.com:587
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smtpd_sasl_auth_enable = yes
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smtpd_sasl_path = smtpd
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smtp_use_tls = yes
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smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
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smtp_sasl_type = cyrus
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smtp_sasl_auth_enable = yes
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# optional: necessary if email provider uses load balancing and
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# forwards emails to another smtp server
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# for delivery (ie: smtp.yahoo.com --> smtp.phx.1.yahoo.com)
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smtp_cname_overrides_servername = no
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# optional: necessary if email provider
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# requires passwords sent in clear text
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smtp_sasl_security_options = noanonymous
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canonical_maps = hash:/etc/postfix/canonical
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</pre>
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additionally we need to know the server and email-address as well as the password to use
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<pre><code class="bash">
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vim /etc/postfix/sasl_passwd
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</code></pre>
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<pre>
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mail.example.com:587     mailadr@example.com:password
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</pre> 
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The above server hostname and port must exactly match the value for "relayhost" in /etc/postfix/main.cf.
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Generate a postfix lookup table from the previous file
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<pre><code class="bash">
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postmap hash:/etc/postfix/sasl_passwd
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</code></pre>
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Test the lookup table, if all is good then the following will return the specified username:password
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<pre><code class="bash">
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postmap -q mail.example.com:587 /etc/postfix/sasl_passwd
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</code></pre>
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next is to bind the local username to the email-address. You may also have a look into @/etc/aliases@ and check who's mail are sent to whom.
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<pre><code class="bash">
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vim /etc/postfix/canonical
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</code></pre>
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<pre>
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root     mailadr@example.com
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</pre> 
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The above email-address must exactly match the email-address in sasl_passwd.
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Generate a postfix lookup table from the previous file
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<pre><code class="bash">
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postmap hash:/etc/postfix/canonical
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</code></pre>
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Make sure that sasl_passwd and sasl_passwd.db files are readable/writeable only by root
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<pre><code class="bash">
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chmod 600 /etc/postfix/sasl_passwd
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chmod 600 /etc/postfix/sasl_passwd.db
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</code></pre>
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Add postfix to be started at boot
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<pre><code class="bash">
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chkconfig --add postfix
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</code></pre>
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h2. Test postfix
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Fire up Postfix
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<pre><code class="bash">
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/etc/init.d/postfix start
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</code></pre>
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Test it out using sendmail alias from the command prompt
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<pre><code class="bash">
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sendmail email@any.com
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Postfix is good to go.
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.
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</code></pre>