DomainKeys Identified Mail (DKIM) lets an organization take responsibility for a message that is in transit. The organization is a handler of the message, either as its originator or as an intermediary. Their reputation is the basis for evaluating whether to trust the message for further handling, such as delivery. Technically DKIM provides a method for validating a domain name identity that is associated with a message through cryptographic authentication.
Sender Policy Framework (SPF) is an email validation system designed to prevent email spam by detecting email spoofing, a common vulnerability, by verifying sender IP addresses. SPF allows administrators to specify which hosts are allowed to send mail from a given domain by creating a specific SPF record (or TXT record) in the Domain Name System (DNS). Mail exchangers use the DNS to check that mail from a given domain is being sent by a host sanctioned by that domain's administrators.[1]
Principles of operation
The Simple Mail Transfer Protocol permits any computer to send email claiming to be from any source address. This is exploited byspammers who often use forged email addresses, making it more difficult to trace a message back to its sender, and easy for spammers to hide their identity in order to avoid responsibility. Many believe that the ability for anyone to forge sender addresses is a security flaw in modern SMTP.
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