Config postfix smarthost » Historie » Revision 2
Revision 1 (Jeremias Keihsler, 04.02.2020 10:21) → Revision 2/3 (Jeremias Keihsler, 21.10.2021 08:42)
h1. Setting up Postfix to send mails via external mail-account h2. Preliminary note See also: * https://www.zulius.com/how-to/set-up-postfix-with-a-remote-smtp-relay-host/ * http://rs20.mine.nu/w/2011/07/gmail-as-relay-host-in-postfix/ 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. h2. Install postfix Should be preinstalled, as it is the default mail-handler with CentOS <pre><code class="bash"> dnf yum install postfix cyrus-sasl cyrus-sasl-gssapi cyrus-sasl-plain </code></pre> h2. configure postfix <pre><code class="bash"> vim /etc/postfix/main.cf </code></pre> <pre> # line ~118... myorigin = example.com # Set this to your email provider's smtp server. # A lot of ISP's (ie. Cox) block the default port 25 # for home users to prevent spamming. So we'll use port 80 # line ~339... relayhost = mail.example.com:587 # add at end of file... smtpd_sasl_auth_enable = yes smtpd_sasl_path = smtpd smtp_use_tls = yes smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd smtp_sasl_type = cyrus smtp_sasl_auth_enable = yes # optional: necessary if email provider uses load balancing and # forwards emails to another smtp server # for delivery (ie: smtp.yahoo.com --> smtp.phx.1.yahoo.com) smtp_cname_overrides_servername = no # optional: necessary if email provider # requires passwords sent in clear text smtp_sasl_security_options = noanonymous canonical_maps = hash:/etc/postfix/canonical </pre> additionally we need to know the server and email-address as well as the password to use <pre><code class="bash"> vim /etc/postfix/sasl_passwd </code></pre> <pre> mail.example.com:587 mailadr@example.com:password </pre> The above server hostname and port must exactly match the value for "relayhost" in /etc/postfix/main.cf. Generate a postfix lookup table from the previous file <pre><code class="bash"> postmap hash:/etc/postfix/sasl_passwd </code></pre> Test the lookup table, if all is good then the following will return the specified username:password <pre><code class="bash"> postmap -q mail.example.com:587 /etc/postfix/sasl_passwd </code></pre> 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. <pre><code class="bash"> vim /etc/postfix/canonical </code></pre> <pre> root mailadr@example.com </pre> The above email-address must exactly match the email-address in sasl_passwd. Generate a postfix lookup table from the previous file <pre><code class="bash"> postmap hash:/etc/postfix/canonical </code></pre> Make sure that sasl_passwd and sasl_passwd.db files are readable/writeable only by root <pre><code class="bash"> chmod 600 /etc/postfix/sasl_passwd chmod 600 /etc/postfix/sasl_passwd.db </code></pre> Add postfix to be started at boot <pre><code class="bash"> systemctl enable postfix </code></pre> h2. Test postfix Fire up Postfix <pre><code class="bash"> systemctl start postfix </code></pre> Test it out using sendmail alias from the command prompt <pre><code class="bash"> sendmail email@any.com Postfix is good to go. . </code></pre>