The acronym DKIM stands for “Domain Keys Identified Mail”. It is an encryption authentication method that is used by many ISPs to establish if the email originated from an authorized system and prevents spammers from stealing the identity of legitimate entities.
DKIM allows for a unique signature to be added to the message header for each email you send. This signature is specific for your domain and is generated by a private key. The corresponding public key is added to a DNS record for your domain.
When an email server receives your email, it checks the public key to determine if your private key was used to generate the email signature. If your private key was not used, the email is considered to be a phishing or spam attempt.
What do I need to do?
You will need to customize your DNS records. Don’t worry, it will only take a few minutes and you can follow our step-by-step guide at: SPF & DKIM Authentication.
Using a free webmail account (Google, Yahoo, etc)? Sorry to tell you this but it is not possible to customize the SPF & DKIM records for Gmail, Hotmail, Yahoo or any other free webmail accounts. You should consider using an email address linked to your website instead.