message was sent from a legitimate sender. However, the main phishers' intent is to compromise user personal and financial information, while spoofing emails is just one of the ways they use to do so. The effect on mail servers Traditionally, mail servers could accept a mail item, then later send a Non-Delivery Report or "bounce" message if it couldn't be delivered or had been quarantined for any reason. These would be sent to the "MAIL FROM:" aka "Return Path" address. With the massive rise in forged addresses, best practice is now to not generate NDRs for detected spam, viruses etc. but to reject the email during the SMTP transaction. When mail administrators fail to take this approach, their systems are guilty of sending "backscatter" emails to innocent parties - in itself a form of spam - or being used to perform "Joe job" attacks. Countermeasures The SSL/TLS system used to encrypt server-to-server email traffic can also be used to enforce authentication, but in practice it is seldom used, and a range of other potential solutions have also failed to gain traction. A number of defensive systems have come into wide use, including: Sender Policy Framework (SPF) an email authentication method designed to detect forging sender addresses during the delivery of the email. DomainKeys Identified Mail (DKIM) an email authentication method designed to detect forged sender addresses in email (email spoofing), a technique often used in phishing and email spam. Domain-based Message Authentication, Reporting and Conformance (DMARC) an email authentication protocol. It is designed to give email domain owners the ability to protect their domain from unauthorized use, commonly known as email spoofing. The purpose and primary outcome of implementing DMARC is to protect a domain from being used in business email compromise attacks, phishing emails, email scams and other cyber threat activities. To effectively stop forged email being delivered, the sending domains, their mail servers, and the receiving system all need to be configured correctly for these higher standards of authentication. Although their use is increasing, estimates vary widely as to what percentage of emails have no form of domain authentication: from 8.6% to "almost half". For this reason, receiving mail systems typically have a range of settings to configure how they treat poorly-configured domains or email. Business email Business email compromise attacks are a class of cyber crime that use email fraud to attack commercial, government and non-profit organizations