DKIM is a way to digitally sign your email so that an outside party can authenticate the message as coming from you. You have to contact Sign-up.to and fill out a form for them to get in touch with you, which is necessary in order to complete this process.
Additionally, lookup and validate your published record using a free DKIM record lookup tool to ensure that your DKIM DNS records are devoid of errors and fully functional.
Enable DMARC for your domains by taking a free DMARC trial to stay abreast of domain spoofing and phishing attacks.
