DKIM - What and Why?

What is DKIM?
DKIM (DomainKeys Identified Mail) is the highest level of email authentication, through the use of cryptographic authentication. It allows the sender to claim responsibility for the message via digital signature, and the receiver to check the public key for the DNS to verify the signature.
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Why is DKIM important for email?
DKIM provides a greater level of authentication than SPF alone and is highly recommended to be used in tandem with SPF. It provides additional 'proof' that messages are legitimate, aiding in deliverability. Though still optional, it may soon be required to take part in certification / accreditation services.

For more reading/information on DKIM, please click here.

To test your DKIM record after implementing, click here.