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Paul Howard
Works at JBS Technologies
Attends Open University
Lives in Copthorne, UK
179 followers|155,841 views


Paul Howard

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Fantastic trip to the Weald and Download museum today.
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Finally fixed the PHP errors so is working again.
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Say hello to Mrs. Howard & kisses to both ur missus!! ^.^
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Charlotte Howard was tagged in Paul Howard's photo.

Paul Howard

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Charlotte is looking more like me all the time.
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It really is quite scary. 
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Another job I now don't have to do :)
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Paul Howard

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Looking for interesting bars/pubs to visit in the west end this weekend.
Been ages since I went out in London.
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Merry Christmas to you and your family, by the power of greyskull!
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We recently worked with a client to set up SPF ( and DKIM ( records for several domains that they send emails from, on behalf of third parties.

Although not a difficult task, while searching the Internet for issues people may  have faced, there did not appear to be a single website that gave clear, concise and most importantly full instructions on how to go about setting up a Linux (in this case Ubuntu) server running postfix to sign outgoing emails with DKIM signatures.

So below you will find the configuration that we used and tested successfully across a number of domains. (all command are running as root so add sudo if necessary in your environment)

1. Make sure all software is up to date

apt-get update
apt-get upgrade

2. Install opendkim

apt-get install opendkim opendkim-tools

3. Set up a directory for the storage of private keys. You can have as many domains as you wish. Change owner and permissions to the opendkim user.

mkdir -pv /etc/opendkim/
chown -Rv opendkim:opendkim /etc/opendkim
chmod go-rwx /etc/opendkim/*

4. Every single domain should have a key pair and appropriate security. Navigate to the appropriate folder and generate a key pair. Change the owner to the opendkim user.

cd /etc/opendkim/ opendkim-genkey -r -h rsa-sha256 -d -s yourtag
chown opendkim:opendkim *
chmod u=rw,go-rwx *

5. Publish the public key using a DNS  TXT record for the domain in question. (key shortened here for space) IN TXT "v=DKIM1;p=AySFjB......xorQAB"

Once set up check it is showing in DNS. From the command line of the email server:

dig TXT

6. Set up the key table.

Open up your text editor of choice and open or create /etc/opendkim/KeyTable file with the following text

7. Set up the signing table. Again, open or create /etc/opendkim/SigningTable in your favorite text editor and enter the following text.


8.  Set up the TrustedHosts file. Open or create /etc/opendkim/TrustedHosts  This will need to contain all the IP ranges that you will allow to use this MTA to sign emails with DKIM in the following format.

9. Next, set up the ownership of files we created to the opendkim user.

chown opendkim:opendkim /etc/opendkim/KeyTable
chown opendkim:opendkim /etc/opendkim/SigningTable
chown opendkim:opendkim /etc/opendkim/TrustedHosts

10. Open /etc/opendkim.conf using your text editor. Make sure the following settings are changed/added. Some ay be present already.

# Enable Logging
Syslog yes
SyslogSuccess yes
LogWhy yes

# User mask
UMask 002

# Always oversign From (sign using actual From and a null From to prevent malicious signatures header fields (From and/or others) between the signer and the verifier)

OversignHeaders From

# Our KeyTable and SigningTable
KeyTable refile:/etc/opendkim/KeyTable
SigningTable refile:/etc/opendkim/SigningTable

# Trusted Hosts
ExternalIgnoreList /etc/opendkim/TrustedHosts
InternalHosts /etc/opendkim/TrustedHosts

# Hashing Algorithm
SignatureAlgorithm rsa-sha256

# Auto restart when the failure occurs. CAUTION: This may cause a tight fork loops
AutoRestart Yes

# Set the user and group to opendkim user
UserID opendkim:opendkim

# Specify the working socket
Socket inet:8891@localhost

11. Configure the OpenDKIM filter on Postfix.

Open /etc/postfix/ and add/uncomment these lines:

# OpenDKIM
milter_default_action = accept
milter_protocol = 2
smtpd_milters = inet:localhost:8891
non_smtpd_milters = $smtpd_milters

12. Restart opendkim and postfix

service opendkim start

service postfix restart

And that is it. Any emails being passed through this MTA with a sending domain that matches those listed in the SigningTable will have a DKIM signature attached.

The easiest way to test everything is working as it should be is to send an email to a Gmail account and look at the original version of the email. It will show you if the DKIM policy has passed and if not hopefully give you some information on what went wrong.
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You guys are enticing me back into code...>.<
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Paul Howard

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One of my favourite  black and white "selfies"
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Back from a fantastic day out in Brighton. Not sure how Charlotte sat in the sea. It was freezing.
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That appears to be a look of horror on her face.
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In his circles
200 people
Have him in circles
179 people
Steve Herbert's profile photo
Martin Saunders's profile photo
Technology consultant and photographer.
  • JBS Technologies
    Owner/Director, 2010 - present
  • Custom iTV
    Head of Group IT, 2001 - 2010
  • Titan Analysis
    Owner/Director, 1997 - 2001
  • Vodafone Group Plc
    IT Support Manager, 1996 - 1997
  • Aztec Rentals
    Technical Manager, 1995 - 1996
  • First Point
    Senior Support Engineer, 1993 - 1995
  • Royal and Sun Alliance
    IT Support, 1988 - 1993
Map of the places this user has livedMap of the places this user has livedMap of the places this user has lived
Copthorne, UK
Maidenbower, Crawley, UK - Mobile, AL, 36609 - Tilgate, Crawley, UK - Broadfield, Crawley, UK - Furnace Green, Crawley, UK - Southgate, Crawley, UK - Horsham, UK - Langley Green, Crawley, UK - Billingshurst, UK - Ifield, Crawley, UK - Bewbush, Crawley, UK - Gossops Green, Crawley, UK
Contact Information
+44 (0)845 805 9232
Apps with Google+ Sign-in
standard nerd

Paul is a writer, photographer, content producer and small business owner.

Paul lives in a small village in Sussex with his wife, Laura, and their daughter. He spends as much time as he can not doing housework and pretending his small garden really does require a large, gas powered BBQ.

For employment, he runs an IT consulting and support companytakes interesting photographs and is in the process of starting up a small media company to produce audio and video podcasts.



Having been in the IT industry since mid 1988, Paul founded JBS Technologies in 2010 to provide SMEs with technical support and IT strategy advice.


Other things to know:

Paul does not own cats for a variety of reasons.

Paul is a Liberal Conservative with far left leanings.

  • Open University
  • Holy Trinity CofE School
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Paul Howard's +1's are the things they like, agree with, or want to recommend.
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A nice change from the usual type of eatery in Crawley. The food is excellent, especially the steak burger. The staff are friendly and helpful and the prices are lower than you would expect. One of my favorite places to grab a quick breakfast or lunch.
Food: ExcellentDecor: ExcellentService: Excellent
Public - a year ago
reviewed a year ago
Very friendly service, and the food was amazing. The portions are huge though so beware of what you order. I doubt I could finish most of the meals on the menu, especially as they all came with a large banana muffin as well. No waiting for coffee refills as they give you a thermal carafe for the table. Being given a free local paper when you are seated is also a nice touch. If you are staying in Vegas you have to try this place at least once.
Food: ExcellentDecor: ExcellentService: Excellent
Public - a year ago
reviewed a year ago
32 reviews
Great value food and good service.
Public - 2 years ago
reviewed 2 years ago
Public - 3 years ago
reviewed 3 years ago