{"id":1135,"date":"2017-02-21T09:11:31","date_gmt":"2017-02-21T03:41:31","guid":{"rendered":"https:\/\/pheonixsolutions.com\/blog\/?p=1135"},"modified":"2019-11-05T17:39:20","modified_gmt":"2019-11-05T12:09:20","slug":"dkim-setup-postfix-mailserver-centos-6-7","status":"publish","type":"post","link":"https:\/\/pheonixsolutions.com\/blog\/dkim-setup-postfix-mailserver-centos-6-7\/","title":{"rendered":"Dkim Setup on Postfix Mailserver – Centos 6\/7"},"content":{"rendered":"

Date Posted:22-02-2017<\/strong><\/p>\n

Its a biggest challenge for a new mail server to reach popular mail provider user’s inbox. One of the best way is to sign the outgoing mail server using dkim. There are multiple ways to implement dkim signing. We are going to use opendkim
\n<\/em>as a service to sign the mail and postfix as a mailserver.<\/p>\n

Assumption:<\/h5>\n
    \n
  1. Centos operating system.<\/li>\n
  2. PostFix Mailserver<\/li>\n<\/ol>\n

    Default installation of postfix would be sufficient.<\/p>\n

    Implementation:<\/h5>\n

    Starts with installing epel repo to the server. Some server may have epel repo already enabled.<\/p>\n

    For Centos 6:<\/strong><\/p>\n

    wget http:\/\/download.fedoraproject.org\/pub\/epel\/6\/x86_64\/epel-release-6-8.noarch.rpm
    \nrpm -ivh epel-release-6-8.noarch.rpm<\/code><\/p>\n

    For Centos 7:<\/strong><\/p>\n

    wget https:\/\/dl.fedoraproject.org\/pub\/epel\/epel-release-latest-7.noarch.rpm<\/code><\/p>\n

    yum install epel-release-latest-7.noarch.rpm (or)<\/code><\/p>\n

    rpm -ivh epel-release-latest-7.noarch.rpm<\/code><\/p>\n

    Install opendkim application using yum<\/p>\n

    yum install opendkim<\/code><\/p>\n

    Delete all the content of \/etc\/opendkim.conf and add only the quoted text mentioned below.<\/p>\n

    vi \/etc\/opendkim.conf<\/code><\/p>\n

    AutoRestart             Yes
    \nAutoRestartRate         10\/1h
    \nLogWhy                  Yes
    \nSyslog                  Yes
    \nSyslogSuccess           Yes
    \nMode                    sv
    \nCanonicalization        relaxed\/simple
    \nExternalIgnoreList      refile:\/etc\/opendkim\/TrustedHosts
    \nInternalHosts           refile:\/etc\/opendkim\/TrustedHosts
    \nKeyTable                refile:\/etc\/opendkim\/KeyTable
    \nSigningTable            refile:\/etc\/opendkim\/SigningTable
    \nSignatureAlgorithm      rsa-sha256
    \nSocket                  inet:8892@localhost
    \nPidFile                 \/var\/run\/opendkim\/opendkim.pid
    \nUMask                   022
    \nUserID                  opendkim:opendkim
    \nTemporaryDirectory      \/var\/tmp<\/p><\/blockquote>\n

    Create keys for the domain. Replace domain.tld <\/em>with our domain name.<\/p>\n

    mkdir \/etc\/opendkim\/keys\/domain.tld
    \nopendkim-genkey -D \/etc\/opendkim\/keys\/domain.tld\/ -d domain.tld -s default
    \nchown -R opendkim: \/etc\/opendkim\/keys\/domain.tld
    \nmv \/etc\/opendkim\/keys\/domain.tld\/default.private \/etc\/opendkim\/keys\/domain.tld\/default<\/code><\/p>\n

    Open the file \/etc\/opendkim\/KeyTable <\/em> and add the following content.<\/p>\n

    vi \/etc\/opendkim\/KeyTable<\/code><\/p>\n

    default._domainkey.domain.tld domain.tld:default:\/etc\/opendkim\/keys\/domain.tld\/default<\/p><\/blockquote>\n

    Open the file  \/etc\/opendkim\/SigningTable <\/em> and add the below lines. * represents all the email accounts associated with domain.tld.<\/p>\n

    vi \/etc\/opendkim\/SigningTable<\/code><\/p>\n

    *@domain.tld default._domainkey.domain.tld<\/p><\/blockquote>\n

    Add the trusted hosts to the file \/etc\/opendkim\/TrustedHosts<\/em><\/p>\n

    vi \/etc\/opendkim\/TrustedHosts<\/code><\/p>\n

    domain.tld<\/p><\/blockquote>\n

    Repeat the same steps if you want opendkim to sign the different domains.<\/p>\n

    Now, the final steps to add the DNS record on the Nameserver<\/em>. We need to add TXT record on the nameserver of the domain.tld.<\/p>\n

    cat \/etc\/opendkim\/keys\/domain.tld\/default.txt<\/code><\/p>\n

    default._domainkey    IN    TXT    ( “v=DKIM1; k=rsa; ”
    \n“p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCzkmrP3nbiXJNXU4UKAJAQX9JPtKhe5+EgfWkkc4mUsFfftGyKMW3oNkM40qldg4XhazCbW1BruQKaXwH\/qWSGdFBQMem9ytF+xZwLDraNKVtRto9bPBpf+VEU34t3Pwarm179\/anahErnSIWENfAeP\/nWrf5qIHBjwsTtF59XgwIDAQAB” )<\/p><\/blockquote>\n

    DNS changes normally requires 12 to 24 hours to reflect all over the world.<\/p>\n

    We can verify the DNS changes using the below commands.<\/p>\n

    host -ttxt default._domainkey.domain.tld<\/code><\/p>\n

    dig txt +short default._domainkey.tld<\/code><\/p>\n

    Configure Postfix:<\/h5>\n

    So far, we have installed opendkim and now we are going to integrate opendkim with postfix application<\/p>\n

    Open the configuration \/etc\/postfix\/main.cf and add the opendkim integration code.<\/p>\n

    vi \/etc\/postfix\/main.cf<\/code><\/p>\n

    smtpd_milters           = inet:127.0.0.1:8892
    \nnon_smtpd_milters       = $smtpd_milters
    \nmilter_default_action   = accept
    \nmilter_protocol         = 2<\/p><\/blockquote>\n

    Restart the opendkim, postfix services.<\/p>\n

    service opendkim start
    \nchkconfig opendkim on
    \nservice postfix restart<\/code><\/p>\n

    Verification:<\/h5>\n

    Now, send mail from your domain.tld either using application and check the results on the log.<\/p>\n

     Feb 20 12:12:58 server opendkim[5644]: 5FF7E161215: DKIM-Signature field added (s=default, d=<\/pre>\n
    domain.tld<\/strong><\/p>\n
    )<\/pre>\n
    We can send emails to check-auth@verifier.port25.com <\/em> and you will receive a notification whether dkim signature added or not.<\/p>\n","protected":false},"excerpt":{"rendered":"
    Date Posted:22-02-2017 Its a biggest challenge for a new mail server to reach popular mail provider user’s inbox. One of […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[1019],"tags":[161,286,171],"class_list":["post-1135","post","type-post","status-publish","format-standard","hentry","category-cloud-aws","tag-centos","tag-opendkim","tag-postfix","psol-cat-cloud-aws"],"jetpack_publicize_connections":[],"jetpack_shortlink":"https:\/\/wp.me\/phn2x7-ij","jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/pheonixsolutions.com\/blog\/wp-json\/wp\/v2\/posts\/1135","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pheonixsolutions.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/pheonixsolutions.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/pheonixsolutions.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/pheonixsolutions.com\/blog\/wp-json\/wp\/v2\/comments?post=1135"}],"version-history":[{"count":0,"href":"https:\/\/pheonixsolutions.com\/blog\/wp-json\/wp\/v2\/posts\/1135\/revisions"}],"wp:attachment":[{"href":"https:\/\/pheonixsolutions.com\/blog\/wp-json\/wp\/v2\/media?parent=1135"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/pheonixsolutions.com\/blog\/wp-json\/wp\/v2\/categories?post=1135"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/pheonixsolutions.com\/blog\/wp-json\/wp\/v2\/tags?post=1135"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}