https://wiki.leaky.org/index.php?action=history&feed=atom&title=Postfix 2026-04-13T09:51:27Z Revision history for this page on the wiki MediaWiki 1.30.0 https://wiki.leaky.org/index.php?title=Postfix&diff=369&oldid=prev 2018-10-16T07:33:38Z

<p>Added postfix notes</p> <p><b>New page</b></p><div>== DKIM ==<br /> <br /> DKIM notes copied from https://www.linuxtechi.com/configure-domainkeys-with-postfix-on-centos-7/ (in case they disappear).<br /> <br /> Enable EPEL repo<br /> <br /> # yum install epel-release<br /> <br /> Install OpenDKIM package and generate the default keys<br /> <br /> # yum install -y opendkim<br /> # opendkim-default-keygen<br /> Generating default DKIM keys:<br /> Default DKIM keys for freshdaymall.com created in /etc/opendkim/keys.<br /> #<br /> <br /> In /etc/opendkim/keys/ are two files - default.private (used for signing the emails) and default.txt (public key to be published in DNS). A selector 'default' is created.<br /> <br /> Edit the following config files:<br /> <br /> * /etc/opendkim.conf<br /> <br /> Mode sv<br /> Socket inet:8891@127.0.0.1<br /> Canonicalization relaxed/simple<br /> Domain ''yourdomain.com''<br /> #KeyFile /etc/opendkim/keys/default.private<br /> KeyTable refile:/etc/opendkim/KeyTable<br /> SigningTable refile:/etc/opendkim/SigningTable<br /> ExternalIgnoreList refile:/etc/opendim/TrustedHosts<br /> InternalHosts refile:/etc/opendkim/TrustedHosts<br /> <br /> * /etc/opendkim/KeyTable<br /> <br /> default._domainkey.''yourdomain.com'' ''yourdomain.com'':default:/etc/opendkim/keys/default.private<br /> <br /> * /etc/opendkim/SigningTable<br /> <br /> *@''yourdomain.com'' default._domainkey.''yourdomain.com''<br /> <br /> * /etc/opendkim/TrustedHosts<br /> <br /> 127.0.0.1<br /> ''host.yourdomain.com''<br /> ''yourdomain.com''<br /> <br /> Add the following three lines to the end of /etc/postfix/main.cf<br /> <br /> smtpd_milters = inet:127.0.0.1:8891<br /> non_smtpd_milters = $smtpd_milters<br /> milter_default_action = accept<br /> <br /> Restart all the services<br /> <br /> systemctl start opendkim<br /> systemctl enable opendkim<br /> systemctl restart postfix<br /> <br /> Add the contents of /etc/opendkim/keys/default.txt to the DNS for ''yourdomain.com'' and make sure that the zone has been reloaded.<br /> <br /> Send a test email:<br /> <br /> # sendmail -fyou@yourdomain.com -t<br /> To: you@externaldomain.com<br /> From: you@yourdomain.com<br /> Subject: DKIM test with Postfix MTA<br /> <br /> Test<br /> .<br /> <br /> Check the maillog:<br /> <br /> Oct 15 13:07:11 host opendkim[3530]: 34D25401AE: DKIM-Signature field added (s=default, d=yourdomain.com)<br /> <br /> Testing it:<br /> <br /> Try the site at http://www.appmaildev.com/en/dkim/<br /> <br /> == Configure Postfix to block outgoing email to all but one domain ==<br /> <br /> This is useful on demo systems where you don't want to be sending most email but still require the ability to send emails to a particular domain or two.<br /> <br /> The correct way is to use Transport Mapping. Check &lt;code&gt;/etc/postfix/main.cf&lt;/code&gt; for a transport_maps option. If there is one already, make a note of the filename in use and substitute that in the rest of these instructions. If there isn't one, add the following to main.cf<br /> <br /> transport_maps = hash:/etc/postfix/transport<br /> <br /> CentOS7 Postfix ships with a template transport file - either replace or append:<br /> <br /> yourdomain.com :<br /> localhost :<br /> * discard:<br /> <br /> This will allow emails to localhost or yourdomain.com but nowhere else. You'll see in /var/log/maillog the process postfix/discard instead of postfix/smtp when dropping emails. Add whatever other domains might be required to the file. If you want a bounce, you can use something like this instead of &lt;code&gt;* discard:&lt;/code&gt;<br /> <br /> * error:Outgoing mail blocked<br /> <br /> Rebuild the transport hash using:<br /> <br /> postmap /etc/postfix/transport<br /> <br /> After changing the config, restart the postfix service - this is not required if you're just changing the transport map.<br /> <br /> service postfix restart</div>

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