DomainKeys Identified Mail (DKIM) records are used by the email receiver to verify the source of the email and detect email spoofing. It works by digitally signing each email with a private key which the receiver can verify using the public key in your DKIM record. This adds certainty that the received email is sent from the domain it claims. You can learn more about DKIM records in this Wikipedia article.
Example DKIM record:
DKIM-Signature: v=1; a=rsa-sha256; d=example.net; s=brisbane;
c=relaxed/simple; q=dns/txt; l=1234; t=1117574938; x=1118006938;
h=from:to:subject:date:keywords:keywords;
bh=MTIzNDU2Nzg5MDEyMzQ1Njc4OTAxMjM0NTY3ODkwMTI=;
b=dzdVyOfAKCdLXdJOc9G2q8LoXSlEniSbav+yuU4zGeeruD00lszZ
VoG4ZHRNiYzR
There are two ways to add a DKIM record to your domain:
SiteHost supports DKIM through a TXT record entry in our DNS Zones module.
default._domainkey.mydomain.co.nz
with the CNAME alias from your provider.
dig +noall +answer default._domainkey.mydomain.co.nz TXT
default._domainkey.mydomain.co.nz. 300 IN TXT "k=rsa; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA1Kd87/UeJjenpabgbFwh+eBCsSTrqmwIYYvywlbhbqoo2DymndFkbjOVIPIldNs/m40KF+yzMn1skyoxcTUGCQs8g3FgD2Ap3ZB5DekAo5wMmk4wimDO+U8QzI3SD0" "7y2+07wlNWwIt8svnxgdxGkVbbhzY8i+RQ9DpSVpPbF7ykQxtKXkv/ahW3KjViiAH+ghvvIhkx4xYSIc9oSwVmAl5OctMEeWUwg8Istjqz8BZeTWbf41fbNhte7Y+YqZOwq1Sd0DbvYAD9NOZK9vlfuac0598HY+vtSBczUiKERHv1yRbcaQtZFh5wtiRrN04BLUTD21MycBX5jYchHjPY/wIDAQAB"
{signing domain}.{selector}
. For the example above, set it as default._domainkey
(see screenshot).