DKIM

DKIM stands for "DomainKeys Identified Mail," a form of email authentication designed to protect email users from spam and other nefarious practices, such as phishing, by verifying the legitimacy of the organizations sending the messages.

Due to the rise of spam in the 1990s and 2000s as the Internet advanced, security measures were developed to protect email users better and authenticate legitimate messages sent by email senders. DKIM is one specification created to help authenticate emails, along with the SPF and DMARC specifications.

DKIM was created in 2004 when the Domain Keys specification developed by Yahoo merged with the Identified Internet Mail specification developed by Cisco. It was then adopted by many ISPs, including AOL, Microsoft, Yahoo, and Google.

DKIM is a digital signature for an email, which allows the message to be authenticated. The digital signature is added to the email message's header, then validated against a public cryptographic key in the Domain Name System (DNS) records of the organization sending the message.

Actual email users will not see traces of DKIM. Instead, the inbound mail server verifies that the domain owner legitimately sent the message before the user receives the message.

DKIM is especially important for businesses sending marketing emails. Without providing the proper credentials, their messages will not be authenticated and delivered to their potential customers.