What is the DKIM and SPF settings meant for?

Domain Keys Identified Mail (DKIM) is a form of email authentication used to verify a sender's identity. By adding a public key to your domain's DNS you allow us to "sign" your message using your domains unique signature. It adds a layer of security behind the scenes that enables providers like Gmail to remove the "via nurturehq.com" message for their users.

Sender Policy Framework (SPF) is a simple email-validation system designed to detect email spoofing by providing a mechanism to allow receiving mail exchangers,to check that incoming mail from a domain comes from a host authorized by that domain's administrators.