I have problem with postfix on debian after upgrading from squeeze to wheezy. Postfix was configured to sign messages using dkim-filter. Before update, everything was working flawlessly, now it fails on connection with service (tcp or unix sockets). I thought that maybe it was because of debian switch to opendkim, so I removed dkim-filter and installed opendkim - same problem. I even tried setting unix file socket connection instead of tcp option - same problem:

postfix/smtpd: warning: connect to Milter service unix:/var/run/opendkim/opendkim.sock: No such file or directory

or (with tcp/ip):

postfix/cleanup: warning: connect to Milter service inet:localhost:8891: Connection refused

I checked twice - socket file exists and service was listening on port 8891.

What can I do to fix this?


10 Answers 10

  1. Check if opendkim is running. (I assume it is as you saw the socket file.)
  2. Did you configure opendkim? The configuration file is /etc/opendkim.conf.

    You need to update the file to match your site/domain and dkim.key path.

  3. Add postfix to opendkim group

    If opendkim.sock permission is as follow

    $ ls -l /var/run/opendkim
    -rw-rw-r-- 1 opendkim opendkim 6 May  2 14:56 opendkim.pid
    srwxrwxr-x 1 opendkim opendkim 0 May  2 14:56 opendkim.sock

    If Not, make sure UMask is set to 0002 in /etc/opendkim.conf.

    Then do the following

    sudo adduser postfix opendkim
  4. Postfix running in chroot

    Modify /etc/default/opendkim, change SOCKET option to postfix chroot location


    You will have to create directory /var/spool/postfix/var/run/opendkim and change its permission

    sudo mkdir -p /var/spool/postfix/var/run/opendkim
    sudo chown opendkim:opendkim /var/spool/postfix/var/run/opendkim
  5. Restart opendkim

    sudo service opendkim restart
  • 4
    I found a similar problem caused by overly restrictive permissions on the opendkim directory. Commented May 17, 2015 at 1:18
  • 1
    I'm sure I had opendkim working before, but noticed that it wasn't working after upgrading from Ubuntu 15.04 to 15.10. Updating socket path in /etc/default/opendkim to the same one I had already defined in /etc/opendkim.conf fixed it. Thanks!
    – Haprog
    Commented Feb 28, 2016 at 11:52
  • my problem is I'm running postfix in chroot and I'm using unix socket. If you see No such file or directory that mean postfix cannot find the path, but it looked for the socket inside /var/spool/postfix/var/run/opendkim/, not /var/run/opendkim Commented Feb 8, 2017 at 7:36
  • @HVNSweeting Isn't that covered in (4)?
    – John Siu
    Commented Feb 9, 2017 at 14:46
  • it is, that why I comment and upvoted instead of create new answer. The question contains so many problems, because if opendkim configured properly, then TCP socket should work. Thank you Commented Feb 10, 2017 at 4:41

Quick summary that helped me to fix this warning on Ubuntu 16.04 LTS: Postfix version 3.1.0-3ubuntu0.2 Opendkim version 2.10.3-3build1

  • (I assume that Postfix and Opendkim are already installed, integrated with each other and the only warning you are getting is 'connect to Milter service local:/var/spool/postfix/opendkim/opendkim.sock: No such file or directory')

  • Add user postfix to group opendkim (skip if already done)

sudo adduser postfix opendkim

  • Create directory and set owner (skip if already done)

sudo mkdir -p /var/spool/postfix/var/run/opendkim

sudo chown opendkim:opendkim /var/spool/postfix/var/run/opendkim

  • Check permissions:

ls -l /var/spool/postfix/var/run/opendkim

srwxrwxr-x 1 opendkim opendkim 0 Nov 12 14:34 opendkim.sock
  • Edit opendkim configuration files: /etc/opendkim.conf, add line

Socket local:/var/spool/postfix/var/run/opendkim/opendkim.sock

/etc/defaults/opendkim, add


  • Edit postfix configuration: /etc/postfix/main.cf
# Milter configuration
# Postfix ≥ 2.6 milter_protocol = 6, Postfix ≤ 2.5 milter_protocol = 2
milter_protocol = 6
milter_default_action = accept
smtpd_milters = unix:var/run/opendkim/opendkim.sock
non_smtpd_milters = unix:var/run/opendkim/opendkim.sock
  • Restart services (or reboot)

systemctl restart opendkim

systemctl restart postfix

That's it. I don't know why it's necessary to write

smtpd_milters = unix:var/run/opendkim/opendkim.sock

instead of

smtpd_milters = local:/var/spool/postfix/var/run/opendkim/opendkim.sock

. If somebody knows, explanations are welcome.

  • 4
    If postfix runs with CHROOT, then the config paths are relative to that. You would end up with postfix trying to resolve /var/spool/postfix/var/spool/postfix/var/run/opendkim/opendkim.sock
    – darken
    Commented Jul 15, 2018 at 21:05

I was facing the same issue on Debian stretch, which turned out to be caused by a broken systemd service file for opendkim. See this answer for a solution: https://serverfault.com/a/847442/84962

This fix boils down to:

systemctl daemon-reload
service opendkim restart
  • 2
    I have Ubuntu system, where only this advise helped, while everything else did not work.
    – silpol
    Commented Dec 20, 2017 at 14:08
  • I run 16.04 and /lib/opendkim/opendkim.service.generate doesn't exists
    – Laurent
    Commented Nov 13, 2018 at 22:29
  • 1
    Work fine on Ubuntu 18.04. Thank you.
    – Duque
    Commented Dec 4, 2018 at 17:22
  • This solved my problem on Debian 9.
    – jchook
    Commented Mar 10, 2019 at 18:32
smtpd_milters = unix:var/run/opendkim/opendkim.sock, unix:var/run/opendmarc/opendmarc.sock
non_smtpd_milters = unix:var/run/opendkim/opendkim.sock, unix:var/run/opendmarc/opendmarc.sock

usermod -G opendkim,opendmarc
  • 5
    This would be a much better answer if it included some explanation of How and Why this answers the question. Commented May 4, 2017 at 16:17
  • 3
    Welcome to Unix & Linux! While this code snippet may solve the question, including an explanation really helps to improve the quality of your post. Remember that you are answering the question for readers in the future, not just the person asking now! Please edit your answer to add explanation, and give an indication of what limitations and assumptions apply. Commented May 4, 2017 at 17:53

An alternative would be to disable the chroot, this has security implications:

vi /etc/postfix/master.cf

# service type  private unpriv  chroot  wakeup  maxproc command + args
cleanup   unix  n       -       n       -       0       cleanup

The warnings says postfix/cleanup, so you can deactivate the chroot for this service.


I had a problem because OpenDKIM and Postfix work with the rights of different users and write and read from the same socket.

I added postfix user to opendkim group:

sudo usermod -a -G opendkim postfix

postfix/smtpd: warning: connect to Milter service unix:/var/run/opendkim/opendkim.sock: No such file or directory

Far as this error goes in 2023... postfix is chrooted and expects files paths to be relative to the postfix chroot-root directory.


# Milter configuration
milter_default_action = accept
milter_protocol = 6
smtpd_milters = local:opendkim/opendkim.sock
non_smtpd_milters = $smtpd_milters

connect to Milter service with error:

unix:/clamav/clamav-milter.ctl: Permission denied

This file:

ls -l /var/spool/postfix/clamav
srw-rw---- 1 clamav clamav 0 Apr  4 17:59 clamav-milter.ctl


user clamav
MilterSocketGroup postfix
MilterSocketMode 660 

user permissions for the milter

chown postfix:postfix /var/spool/postfix/clamav/clamav-milter.ctl 

Works for me


I got this to work by switching from pid to socket. Add the following two statements in respective files then restart both postfix and opendkim

.........Add this single line here regarding the smtpd_milters...


smtpd_milters = inet:

Unrelated... Other stuff I have in this file you might need...

non_smtpd_milters = $smtpd_milters milter_default_action = accept milter_protocol = 2 smtp_tls_security_level = may smtp_tls_loglevel = 1 policyd-spf_time_limit = 3600

THEN....... in this file...


Add this line....

Socket inet:8891@localhost

Both lines replacing whatever you had


I've got this problem for a long time and used a lot of tutorials to fix it. And now i've found the correction !! I'm posting my config file here and my solution for people who need help like me and also if i've got the same problem an other time.

My solution was : Add localhost.localdomain localhost to /etc/hosts and reboot your server.

You can find here all of my postfix config, you can try to copy it. I used two tutorials to configure my postfix server and opendkim server : https://www.linode.com/docs/guides/email-with-postfix-dovecot-and-mysql/ and https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-dkim-with-postfix-on-debian-wheezy

Config file : /etc/default/opendkim

# Command-line options specified here will override the contents of
# /etc/opendkim.conf. See opendkim(8) for a complete list of options.
# Change to /var/spool/postfix/var/run/opendkim to use a Unix socket with
# postfix in a chroot:
# Uncomment to specify an alternate socket
# Note that setting this will override any Socket value in opendkim.conf
# default:
# listen on all interfaces on port 54321:
# listen on loopback on port 12345:
# listen on on port 12345:
#SOCKET=inet:[email protected]

Config file : /etc/opendkim.conf

Syslog                  yes
UMask                   002
Socket                  inet:12301@localhost
PidFile               /var/run/opendkim/opendkim.pid
OversignHeaders         From
TrustAnchorFile       /usr/share/dns/root.key
Canonicalization        relaxed/simple

ExternalIgnoreList      refile:/etc/opendkim/TrustedHosts
InternalHosts           refile:/etc/opendkim/TrustedHosts
KeyTable                refile:/etc/opendkim/KeyTable
SigningTable            refile:/etc/opendkim/SigningTable

Mode                    sv
PidFile                 /var/run/opendkim/opendkim.pid
SignatureAlgorithm      rsa-sha256

UserID                  opendkim:opendkim

System file : /lib/systemd/system/opendkim.service

Description=OpenDKIM DomainKeys Identified Mail (DKIM) Milter
Documentation=man:opendkim(8) man:opendkim.conf(5) man:opendkim-genkey(8) man:opendkim-genzone(8) man:opend$
After=network.target nss-lookup.target

ExecStart=/usr/sbin/opendkim -P /var/run/opendkim/opendkim.pid -p inet:12301@localhost
ExecReload=/bin/kill -USR1 $MAINPID


I hope i could help you !

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .