What is DKIM?
DKIM (DomainKeys Identified Mail) is kind of validation method for authenticity of email message each sent mail signed using a private key .So when each email is sent by your domain with DKIM record, it is signed using a private key and then validated on the receiving mail server using a public key that is in DNS. This process verifies that the message was not altered during transit,or not a spam emails.
Why DKIM record is important
An emails that are signed with DKIM appear more legitimate to your recipients and are less likely to go to Junk or Spam folders. Passing DKIM is required for “Domain-based Message Authentication, Reporting & Conformance” (DMARC), a newer standard to reduce email spoofing which builds on top of SPF and DKIM.
How does DKIM work
DKIM uses DNS TXT records for domain DNS Zone file with a special format. When a private/public key pair is created, the public key is added to your domain’s DNS, This is the public key in a format for use in a bind 9 zone file e.g for domain example.com