DKIM (DomainKeys Identified Mail)

An email authentication method that adds a digital signature to outgoing messages so receiving mail servers can verify they came from your domain and were not altered.

When DKIM is set up, your email service signs each outgoing message with a private key. You publish the matching public key in your domain's DNS records. Receiving servers use that public key to check the signature, confirming the message genuinely came from an authorized sender for your domain and was not changed along the way.

DKIM is one of the building blocks that helps prevent criminals from sending email that pretends to be from your business. Together with SPF and DMARC, it improves your email deliverability and makes it harder for scammers to impersonate you to clients and suppliers. Major email providers increasingly expect bulk senders to have these records in place, and messages without them are more likely to land in spam.

Practical tip: make sure DKIM is enabled not only for your main email platform, such as Microsoft 365 or Google Workspace, but also for any third-party services that send email on your behalf, like newsletter, invoicing or CRM tools.