DNS/SPF

SPF-DNS - SPF + DK + DKIM with Postfix

Beschreibung

Shows up a detailed process on how to set up SPF + DK + DKIM with Postfix in Plesk 11.5 on Debian Wheezy, step by step, and how to test to make sure everything is working correctly

I leased a dedicated server from Hetzner, and I got the Plesk option, for administration, so I don’t have to bother with administration, but turns out I’m not so lucky, I’ve ran into a lot of issues with using Plesk, so I had to do my own fixes.

So let’s take a look at how we can integrate SPF + DK + DKIM with Postfix in Plesk 11.5 on Debian Wheezy.

First things, first, if you are using QMail switch to Postfix, to install Postfix you can either use the GUI, or you can do it from a console.

Here is how to do it from the console.

/usr/local/psa/admin/sbin/autoinstaller --select-release-current --install-component postfix

SPF

Let’s open the DNS Template, you will see there that, there is an entry for SPF

v=spf1 +a +mx -all

This means the SPF is enabled on our domain.

Let’s modify it a little bit to be better, if you are gonna host multiple domains from your server, then you should probably modify it too.

v=spf1 +a +mx +ip4:<ip.mail> ?all* <ip.mail> - Is the IP of the mail server that is responsible for sending the mails, it is automatically filled in when you apply the zones

After you do this modification you should apply it

So now my configuration looks like this:

"SPF DNS Template"

Now let’s check with dig if the SPF is OK.

dig myserverplace.de TXT @ns1.myserverplace.de

You will see in the Answer section I have the following entry

myserverplace.de. 600 IN TXT "v=spf1 +a +mx +ip4:144.76.163.46 ?all"

So everything is ok, next onto DomainKeys

DomainKeys

DKIM

Postfix

Now let’s see what we need to do to configure Postfix to use OpenDKIM.

Execute the following command to see the milters configured

cat /etc/postfix/main.cf | grep "milters"
smtpd_milters = , inet:127.0.0.1:12768
non_smtpd_milters = , inet:127.0.0.1:12768

You can see that we have additional milters we need to put, this one is from the process psa-pc-remote, and it’s part of Plesk

Open /etc/postfix/main.cf with your favorite editor, and add the following to the end of the file

# OpenDKIM
milter_default_action = accept
milter_protocol = 6
smtpd_milters = , inet:127.0.0.1:8891, inet:127.0.0.1:12768
non_smtpd_milters = $smtpd_milters

As you can see we added the OpenDKIM milter too, and milter_protocol is set to 6, this is important, if it’s not set to 6, the psa-pc-remote process will segfault like so,

psa-pc-remote[18523]: segfault at 0 ip 00007fa5be18c034 sp 00007fa5bccffd30 error 4 in libc-2.13.so[7fa5be123000+180000]

And your messages won’t be signed with DomainKey, only with DKIM

service postfix restart

Testing

There is an easy way to test if everything is correct, create an email account if you haven’t already and send a test mail to the following recepients, and the results are cut down because the text is too big* check-auth@verifier.port25.com

==========================================================
Summary of Results
==========================================================
SPF check: pass
DomainKeys check: pass
DKIM check: pass
Sender-ID check: pass
SpamAssassin check: ham* AAAA3QcKCQwA@appmaildev.com

============================================================
SPF result: Pass
============================================================
Domain: myserverplace.de
IP: 144.76.163.46

SPF Record: myserverplace.de
IN TXT = "v=spf1 +a +mx 144.76.163.46 ?all"

============================================================
DomainKey result: pass
============================================================
Signed by: admin@myserverplace.de

PublicKey: default._domainkey.myserverplace.de
IN TXT = "p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDAruBNqdsSCKBLwMrFNNKH8z0e7zmlAic7iRoJsDDJK3IlnW8j6G/T6a93m+jqYc6R38MBAZbeSv2LQJ0SepJEsr4Iqk41WFXPBKnyXReO1RXPW5/YnRe6dpJMEqsmPpl2TjInY7ve/6VCiVDOHn9RRrdB+x7CGeK2crgqSZVlFwIDAQAB;"

============================================================
DKIM result: pass
============================================================
Signed by: admin@myserverplace.de
Expected Body Hash: frcCV1k9oG9oKj3dpUqdJg1PxRT2RSN/XKdLCPjaYaY=
PublicKey: mail._domainkey.myserverplace.de
IN TXT = "v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDMziMcgPTWK0kSUKxrgHHzEiWxNkZ2/M0Ugyr/8H9WtoCsJUM+Bc1C9VwqJ6yjTidecDrX7aL0lFZ9Mylku/wtSiPw6KLxMg2LG2vrMzlPTB2lmJNmg/EOu3KPC8BtAuOhXfwVH/ttQbzdKJKWqiCJn7jhF5oqEKnOCORxOQXKIwIDAQAB;"

Logs

You can check the following locations to see if there are errors

/var/log/mail.err
/var/log/mail.warn
/var/log/mail.info
/var/log/syslog

Note

Make sure you enable testing mode for DKIM if you plan to test, you can also cut down the EXPIRY time so the results propagate faster, so to enable testing mode set the key _domainkey to t=y; o=-

References