Email Authentication and Protocols Glossary - Everything you need to know

May 26, 2023
Email Authentication and Protocols Glossary - Everything you need to know

We all know how vital email is for communication, from personal to professional needs. However, email security can be compromised by unwanted phishing attacks and spam. Email marketers and individuals alike understand the importance of keeping their communications secure. After all, unauthorized email access can easily compromise the reputation and credibility of businesses and individuals.

Fortunately, there are Email Authentication and Protocol measures designed to ensure that email communication is secure and trustworthy. However, navigating this complex and technical subject can be challenging, particularly for those new to the topic.

Therefore, we've designed an ultimate glossary that will guide you through the concepts and terms associated with these vital measures. From SPF to DMARC, our comprehensive guide is packed with essential information to enable you to protect your emails at all times. Whether you're a pro or just starting, this glossary will undoubtedly become your go-to resource, keeping your communications secure and trustworthy.

Email Authentication and Protocols – why are they important

Email Authentication and Protocols play a fundamental role in modern email communication. They are a set of measures used to verify the authenticity of an email message and ensure that it's coming from a trusted source. Email Authentication and Protocols are vital because they help prevent email-based threats like phishing, spam, and other forms of fraud. 

As an email marketer, imagine sending out your new campaign to thousands of subscribers only to realize later that your messages were labeled as spam or your recipients didn't receive them. By using Email Authentication and Protocols, you can guarantee the delivery of your messages to the right inbox and ensure that your brand reputation remains intact. From SPF to DMARC, the Email Authentication and Protocols landscape can be challenging and complex to navigate, but the effort is worth it when you consider the potential damage of a security breach. By implementing these measures, you can keep your communications secure and protect yourself from email-based threats.

Email Authentication and Protocols Glossary

Email Authentication 


Authentication refers to verifying that an email message comes from the sender it claims to be from. It helps to verify the identity of the sender and ensure that emails are not being sent by scammers or other malicious actors. Common email authentication protocols include SPF, DKIM, and DMARC.


SPF (Sender Policy Framework)  is an email authentication protocol that allows email senders to specify which IP addresses are authorized to send emails from their domain. This helps to prevent spoofing and phishing attacks. SPF works by verifying that the server sending your messages is authorized to do so for your domain name. This ensures that no one else can use your domain name in their own emails without permission. 


DKIM (DomainKeys Identified Mail) is an email authentication protocol that verifies the authenticity of the email sender's domain by adding a digital signature to the email message's header. DKIM uses a combination of public key encryption and DNS records to verify that the email was not modified during transmission and to ensure that the sender's domain is authorized to send emails on its behalf. By enabling DKIM authentication, email marketers can improve email deliverability rates, reduce the risk of their emails being marked as spam or rejected and increase their sender reputation. DKIM authentication is supported by major email providers and is widely used by email service providers to authenticate outbound emails, ensuring that delivery rates are high, and email campaigns are successful.


DMARC (Domain-based Message Authentication, Reporting & Conformance) is an email authentication protocol that helps businesses protect their email domains from unauthorized use or fraudulent emails. DMARC works by using both SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) protocols to verify the authenticity of the sender's domain and email message. By implementing DMARC, email marketers can enforce policies that instruct email providers on how to handle emails that fail authentication. DMARC also provides reporting and visibility back to the email sender about their email authentication performance, allowing them to monitor and improve their email deliverability rates. With DMARC, businesses can control their email domain reputation, reduce the risk of email scams and phishing attacks being sent on their behalf, and improve their email deliverability rates.

Sender ID

Sender ID is an email authentication technology that aims to help detect email spoofing. It checks that the email message was sent from an authorized mail server for the domain in the message’s "From" field.


DANE (Domain-based Authentication of Named Entities) is an authentication option that can be used to secure emailed information. It provides an alternative to Certificate Authorities (CA) by allowing domain owners to store their own TLS/SSL certificates in DNS records, improving security while reducing the risk of man-in-the-middle attacks.


MIC (Message Integrity Check) An essential part of email authentication, this security measure ensures that the contents of a message have not been altered while in transit. It verifies that the message has not been tampered with and has arrived at the recipient the same way it was sent.


SRS (Sender Rewriting Scheme) is a protocol used primarily for forwarding email messages that corrects the "From:" address of the original message, allowing the message to pass authentication checks.


SASL (Simple Authentication and Security Layer) is a framework used to authenticate an SMTP (email) server to an email client. It allows email accounts to be secured by requiring users to use their account username and password every time they send or receive email.


ARC (Authenticated Received Chain) is a validation system that allows email forwarding services to preserve authentication results. By affixing a digital signature to messages as they pass through each hop, ARC helps protect messages against unauthorized modification and rejection.


DomainKeys (DK) is an email authentication protocol that verifies the domain name of an email forwarding service before the forwarded email is delivered to the recipient’s email inbox. Additionally, DK helps protect email users from email-based attacks by allowing email receivers to verify the source of an email.


DKIM-ADSP (DomainKeys Identified Mail with Author Domain Signing Practices) is an optional email authentication scheme that permits a domain owner to articulate signature practices they apply to messages that lack a signature. This helps prevent attackers from impersonating the domain owner.


DKIM-ML (DomainKeys Identified Mail with Mailing List Expansion) is a proposed extension to the DKIM standard that allows mailing lists to add additional information to the header of an email message. This helps ensure that messages are signed and authenticated correctly, even when going through mailing lists.


XMPP (Extensible Messaging and Presence Protocol) is an open standard format used for instant messaging and presence information. It provides secure peer-to-peer communication between two or more parties, and its use is being expanded to include VoIP.


TOTP (Time-Based One-Time Password) is a type of two-factor authentication that uses time-based codes and is commonly used in conjunction with mobile applications. It requires both a password and a timed or one-time code generated by a specific algorithm that the user has access to, ensuring strong authentication.


Two-Factor Authentication (2FA) is an additional layer of security used for user authentication. It requires users to provide two types of authentication data to gain access to a computer system or application. In the context of email security, it is highly recommended to reduce the risk of unauthorized access.


U2F (Universal 2nd Factor) is a two-factor authentication standard that provides a secure and easy way to authenticate without relying on passwords. It requires a USB token or NFC-enabled smartphone, providing a simple, secure, and easy-to-use solution.


STARTTLS (START Transport Layer Security) is an email policy method that allows plain text communications to be upgraded to encrypted communications using TLS. This provides improved security for email messages while in transit, helping to protect messages against snooping and interception.

Public Key Cryptography

Public Key Cryptography is a security mechanism that uses a two-key system to encrypt and decrypt messages. The public key encrypts the message, while the private key decrypts it. PKI is widely used in email security because it provides secure key exchange, simplifying key management.


TLS (Transport Layer Security) is a widely used cryptographic protocol that enhances the privacy and security of information on the internet. TLS ensures that network connections are secure, protecting sensitive data from being intercepted and eavesdropped.


Encryption involves the process of converting information or data into an encrypted code, keeping it safe from being accessed or understood by an unauthorized party. It is an essential aspect of email security, allowing for the protection of sensitive and confidential information.

Email Protocols


SMTP (Simple Mail Transfer Protocol) is an internet standard for sending email messages between servers, applications, and other email senders. SMTP is a communication protocol that enables email transfer in a reliable, efficient, and secure manner by specifying how data is transferred and formatted. SMTP is commonly used by email service providers, email marketing platforms, other email senders, and messaging applications. Email messages sent via SMTP must comply with specific formatting rules set forth by email providers, including email header format, content rules, and authentication protocols. By using SMTP, email senders can ensure that their messages are delivered reliably, efficiently, and with high-security protocols.


POP (Post Office Protocol) is a basic method used for email retrieval and delivery. It works by downloading messages from an email server and saving them to a personal computer. While it offers accessibility and easy storage, the downloaded messages are not available on multiple devices and do not remain on the server.


IMAP (Internet Message Access Protocol) is an email protocol that provides the ability to access email messages without downloading them to a personal computer. This allows users to receive and access emails on multiple devices, and all messages stored remain on the server.


MIME (Multipurpose Internet Mail Extensions) MIME is an email content type that allows non-text attachments, such as images, audio, and video files, to be sent and received via email. This extends the functionality of email beyond text-only messages and enhances the user experience.


S/MIME (Secure/Multipurpose Internet Mail Extensions) is a secure method for sending and receiving email messages. It provides end-to-end email message cryptographic security through encryption and digital signing messages.


HTTP (Hypertext Transfer Protocol) is an application-layer protocol used to transmit text, image, video, and other information over the Internet. It is used by email clients to communicate with email servers, exchanging data and messages.


HTTPS  (HTTP Secure)  is an encrypted version of HTTP that securely transmits information over the internet. It uses SSL/TLS encryption to ensure that sensitive information is kept private when it is transferred between a user's web browser and the website's server.


FTP (File Transfer Protocol) is a standard network protocol used to transfer files between computers on the internet. It is commonly used to transfer large files, such as multimedia files and software downloads, to different email servers.


NNTP (Network News Transfer Protocol) is an internet protocol used to read and distribute newsgroup messages over a network. Though used less frequently in today’s world, NNTP was the primary means of internet-based discussions and online communities before chat applications became popular.


SMTP-S (Simple Mail Transfer Protocol Secure) is a protocol that allows secure, encrypted email to be sent through email clients. It encrypts outgoing email messages and requires email servers to have an SSL (Secure Sockets Layer) certificate.


LDAP (Lightweight Directory Access Protocol)is an internet protocol used to access and maintain distributed directory services that house information about users, email accounts, and other system resources in the organization. It is designed to enable simple searches for network information while maintaining network security.


LDAPS (Lightweight Directory Access Protocol Secure) is an email protocol that provides secure data transmission by using the Transport Layer Security (TLS) encryption protocol. It encrypts the data being transferred, making it difficult to intercept or read.


BIMI (Brand Indicators for Message Identification) is an email authentication protocol that allows email marketers to display their brand's logo next to their email messages in the recipient's inbox. If the recipient has not enabled image blocking, their inbox will display the brand's logo beside their email, which can increase brand awareness and trust. BIMI relies on the Domain-based Message Authentication, Reporting & Conformance (DMARC) protocol to authenticate the email sender's domain and logo image file, making it more difficult for email scammers to use brand logos to perpetrate fraudulent activities. Implementing BIMI requires email marketers to follow specific guidelines and requirements, such as having a DMARC policy in place and using an approved BIMI Certification Authority to authenticate their brand logo.


SSL (Secure Sockets Layer) is a security protocol that is used to secure email communications over the Internet. It encrypts the information being sent, making it difficult for unauthorized persons to intercept or read the information.


TLS (Transport Layer Security) is an updated version of SSL and is the standard security protocol for sending and receiving email messages. It encrypts email data in transit, preventing unauthorized access to sensitive information.


ESMTP (Extended Simple Mail Transfer Protocol) is an extended version of Simple Mail Transfer Protocol that provides additional features and functions, such as authentication options, larger message sizes, and more. It is widely used in email services to enhance the abilities of email clients.


SSH (Secure Shell) is a secure network protocol that is used to provide secure remote access to servers. It encrypts data that is transferred between the server and the client, preventing unauthorized access to the data. It is commonly used by email administrators to remotely access and manage email servers.


DNS (Domain Name System) is a protocol that is used on the internet to translate domain names into IP addresses. It is an essential component of the internet infrastructure that enables users to access resources by entering human-readable domain names rather than numerical IP addresses.


DANE (Domain Name System-Based Authentication of Named Entities) is a security protocol that is used to authenticate named entities using DNS. It allows domain owners to store their own TLS/SSL certificates in DNS records, helping to improve security while reducing the risk of man-in-the-middle attacks.


IPsec (Internet Protocol Security) is a protocol suite that is used to secure communications over IP networks. It provides authentication and encryption services to ensure the confidentiality, integrity, and authenticity of information that is transferred between devices over the internet.


IKE (Internet Key Exchange) is a protocol used to establish secure connections for Virtual Private Networks (VPNs) over the Internet. It is responsible for managing resources and negotiating the encryption and authentication methods that will be used during a secure connection.


SASL (Simple Authentication and Security Layer Digest-MD5) is a mechanism used to authenticate a user to a network service. It requires a challenge-response protocol based on a shared secret. It is commonly used with email clients to increase email account security.


SNMP (Simple Network Management Protocol) is a protocol used to manage network devices such as servers, routers, and switches. It provides network administrators with an easy way to monitor and control network resources.


SOAP  (Simple Object Access Protocol) is an XML-based protocol used to exchange structured information over the internet. It enables communication between different systems and provides a messaging framework for expressing web services.

WebSocket Protocol

WebSocket Protocol is a protocol used to provide bidirectional, full-duplex communication over a single TCP connection. It enables real-time communication between web servers and clients and is commonly used in web applications that require frequent updates, such as games and chat applications.

Understanding email protocols is essential for protecting the security and confidentiality of email communications. The various protocols available provide security mechanisms that help prevent unauthorized access and interception of emails by cyber criminals. With the appropriate protocols in place, businesses and individuals can safeguard their email communications and reduce vulnerabilities. It's also important to continually upgrade these protocols to keep up with rapidly evolving cybersecurity threats. With these tools, users can remain confident that their emails are safe and secure, and hackers and cyber criminals cannot gain unauthorized access to sensitive information.

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