DKIM stands for DomainKeys Identified Mail and is a technology used to verify the authenticity of an email message and ensure that it comes from an authorized sender.
DKIM uses digital signatures created at the domain level and embedded in the header of the email message. These signatures are used by recipients to verify whether the email was sent from an authorized server and whether the content of the message remained unchanged during transmission.
By using DKIM, the likelihood of emails being forged or manipulated to be sent as spam or phishing attempts can be reduced. DKIM is one of the technologies used as part of the DMARC (Domain-based Message Authentication, Reporting and Conformance) initiative to improve email security.