DKIM

DomainKeys Identified Mail

Links

• dkim check
• DKIM and postfix
• https://help.ubuntu.com/community/Postfix/dkim-milter Postfix and dkim-milter]
• DKIM Homepage
• http://www.opendkim.org/opendkim-README
• About DKIM
• DKIM with Sendmail
• https://wiki.debian.org/OpenDKIM
• http://www.myiptest.com/staticpages/index.php/DomainKeys-DKIM-SPF-Validator-test
• SPF and DKIM on Debian
• DKIM on relay server

 

OpenDKIM Howto

On Ubuntu you might have to create:

mkdir -p /etc/opendkim/keys
chown -R opendkim.opendkim /etc/opendkim
chmod go-rw /etc/opendkim/keys

Then

cd /etc/opendkim/keys

The 'selector' you choose here does not have to be the actual selector used in DNS. It is just the name used for storing the .txt and .private files

opendkim-genkey -s somename -d domain.name

Make sure the key ends up in /etc/opendkim/keys and is readable for user opendkim, so

chown -R opendkim.opendkim /etc/opendkim/keys

SigningTable

1. somename is the first field in Keytable

*@domain.name somename

KeyTable

Here the name of the selector (the part before ._domainkey) is the one you publish in dns

somename domain.name:selectorname:/path/to/somename.private

Configuration file /etc/opendkim.conf

Mode    s
KeyTable        /etc/opendkim/KeyTable
SigningTable    refile:/etc/opendkim/SigningTable

Postfix

In /etc/postfix/main.cf:

 

milter_protocol = 2
milter_default_action = accept
smtpd_milters = inet:localhost:8891
non_smtpd_milters = inet:localhost:8891

 

Checking

opendkim-testkey -d domain.name -s selectorname -vv -k keys/keyname.private

This will try to fetch the key published in DNS, so "record not found" means DNS record not found. No output is good output.

• https://www.dmarcanalyzer.com/nl/dkim-record-validatie/

WARNING:Unsafe permissions

make readable for user opendkim only

keys do not match

Try

opendkim-testkey -d domain.name -s selectorname -vv

FAQ

opendkim: no signing table match for

In opendkim.conf use:

refile:/etc/opendkim/SigningTable

opendkim-testkey key not secure

Probably means you have no DNSSEC

opendkim-testkey: keys do not match

probably means double check Keytable

opendkim: /etc/opendkim.conf: /etc/opendkim/keys/default.private: open(): No such file or directory

Means it's defined in opendkim.conf, and you're not using KeyTable

 

This doesn't seem to be a valid RSA public key: RSA.xs:178: OpenSSL error: bad base64 decode

??

opendkim.service: Start request repeated too quickly.

Probably rights somewhere, try

opendkim -v