Authentication protocols

Email authentication protocols are standards that verify whether an email was actually sent by the domain it claims to come from. These protocols help prevent spoofing, phishing, and unauthorized sending, and are essential for establishing trust with inbox service providers (ISPs). 

The three main protocols are: 

• SPF (Sender Policy Framework): Confirms that the sending IP is authorized to send mail for the domain. 
• DKIM (DomainKeys Identified Mail): Uses a private/public keypair to cryptographically sign messages on behalf of the sender domain. 
• DMARC (Domain-based Message Authentication, Reporting & Conformance): Builds on SPF and DKIM to provide policy enforcement and reporting. It tells receiving servers what to do when authentication fails. 

Why it matters:  

Without proper authentication, your messages are more likely to be rejected, sent to spam, or flagged as suspicious, no matter how clean your content is. 

Note: Authentication isn’t optional anymore. Major mailbox providers like Gmail and Microsoft increasingly require alignment with SPF, DKIM, and DMARC for consistent inbox placement.