Email Security Protocols: Your Defense Against Online Threats

Email security protocols illustration with mobile phone and locked screen

Over the past few decades, the internet has undergone a remarkable transformation, evolving from a novel technological curiosity into an integral and inseparable part of our daily lives. At the heart of this profound shift is the way we communicate, and in the world of digital messaging, email reigns supreme. The stats back it up; the number of emails sent daily has gone from 12 billion emails in 2000 to 347 billion emails in 2023.

However, as technology brings the world closer, there are also many security issues we have to be aware of. Take, for example, phishing or spoofing emails. They are more prevalent than ever before, with Google blocking over 100 million phishing emails every day.

This is why we need email security protocols — they ensure our private and sensitive information remains confidential and secure. Let’s dive into the world of secure email protocols and how they benefit email marketers.

What are Email Security Protocols?

Email security protocols are a set of standardized rules and practices designed to enhance the security of email communications. These protocols include measures to encrypt email messages, verify the identity of senders and recipients, prevent spam and phishing attacks, and protect against various email-related threats. 

Common email security standards and practices include TLS (Transport Layer Security) for encryption, SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting, and Conformance) for authentication, as well as anti-malware and anti-phishing filters to safeguard against malicious attachments and links. These protocols collectively work to make emails safer and more reliable.

Email Security Protocols: Benefits

Imagine a world without email security protocols — absolutely anyone could access your emails and steal your data.

Let’s review the benefits of having these protocols in place:

  • Confidentiality: Communication encryption protocols, such as TLS, help maintain the privacy of your email content, preventing unauthorized access and eavesdropping and ensuring your sensitive information remains confidential.
  • Authentication: Protocols like SPF, DKIM, and DMARC help verify your authenticity, reducing the risk of email spoofing and phishing attacks. This makes customers trust your email communications; ESPs like Google and Yahoo agree.
  • Integrity: Security protocols protect your email messages from tampering during transmission. Your recipient can be sure the message they received is identical to the one you sent, guaranteeing data integrity.
  • Protection against spyware/malware: Security protocols often include anti-malware filters, which help detect and block malicious attachments or links that can introduce malware into a system. Your subscribers would be pretty mad if you accidentally sent them a virus!
  • Reduced spam: These protocols help reduce the amount of spam and unwanted email by verifying the legitimacy of senders — giving you the green flag as a legitimate email sender.
  • Compliance: Email security protocols on your domain are necessary to meet regulatory and compliance requirements, such as GDPR or CAN-SPAM, ensuring correct handling of sensitive information.
  • Enhanced reputation: By implementing these protocols, you can enhance your email sender reputation, reducing the likelihood of your legitimate emails being marked as spam.
  • Prevention of phishing scams: With authentication and verification mechanisms, security protocols make it more challenging for cybercriminals to pretend to be you and carry out phishing attacks. This reduces the risk of your subscribers falling for scams.

Email security protocols play a vital role in protecting the confidentiality, integrity, and authenticity of your emails. 

The Importance of Email Security Protocols in Email Marketing

In email marketing, where the trust of your recipient is paramount, email security standards are crucial. This is because marketing emails are a lot less personal than workplace or personal emails, and it would greatly annoy subscribers to receive an email that poses a security threat to them. 

But that’s not all.

Let’s look at why you need to take secure email protocols seriously as an email marketer.

  • Email delivery: Implementing email security protocols, such as SPF, DKIM, and DMARC, helps ensure your marketing emails reach your recipients’ inboxes instead of going on a spam list, keeping your email delivery rate up. 
  • Maintaining deliverability: High deliverability rates are crucial for successful email marketing. Implementing security protocols helps boost deliverability rates by ensuring your messages reach your readers. This also improves your open rates and the chances of your intended audience engaging with your messages.
  • Sender authentication: These protocols establish sender authentication, which is crucial in email marketing. When recipients see your emails are properly authenticated, they are more likely to trust you and engage with your content.
  • Data security: Email marketing often involves the collection of customer data. Implementing secure email protocols helps protect this sensitive information and ensures it’s transmitted securely.
  • Tackle phishing risks: Your email campaigns can be targets for phishing attacks if not properly secured. These protocols help prevent attackers from using your brand’s identity for malicious purposes.
  • Compliance: Many email protocols are necessary to comply with data protection and privacy regulations. Ensuring compliance is essential to avoid legal issues and protect your customers’ data.

As part of email best practices, we recommend you add security protocols to both your domain and website. By implementing them, you can improve the effectiveness of your email marketing campaigns and build trust with your audience.

Protect Your Brand Image and Earn Customer Trust With Security Protocols

Secure emails contribute to a positive brand reputation. Protecting your company’s image is essential in email marketing because it can impact the success of your campaigns and how recipients perceive your business.

Secure email communications also help build trust with your customers. When they receive well-authenticated emails, they are more likely to trust your company.

Now that we are aware of the critical role email security protocols have in email marketing, let’s look at the most popular ones in use today.

The Role of SSL/TLS In Email Security

SSL, or TLS as it is known today, plays a crucial role in securing email communication, just as it does for web browsing. In the context of email, TLS provides encryption and offers secure transmission of email messages between clients and servers. 

Let’s take a closer look at the different ways TLS helps your emails reach their destination safely:

  1. Encryption: TLS encrypts the content of your email messages as they travel between email clients and servers. This encryption helps protect the confidentiality of your content, making it difficult for unauthorized parties to intercept and read your messages as they travel over the internet.
  2. Authentication: TLS also facilitates authentication between email servers. When two email servers communicate using TLS, they can verify each other’s identities, verifying that your server is legitimate and your recipient’s server is the intended destination. This helps prevent various email security threats, such as email spoofing and man-in-the-middle attacks.
  3. Secure connections: TLS establishes secure connections between email clients (like Outlook or Thunderbird) and email servers (for example, Gmail or MS Exchange). This ensures protection for the communication between the client and the server against eavesdropping and tampering.
  4. Protection during email relay: Email messages often travel through multiple email servers before reaching their final destination. TLS can be used at each point in the email relay process to ensure the message remains encrypted and secure throughout its journey.
  5. Compliance and regulatory requirements: Many regulations and data protection standards, such as the General Data Protection Regulation (GDPR) and CAN-SPAM, require the use of encryption for sensitive email communications. TLS helps you meet these compliance requirements by securing your email traffic.

With the above features, TLS in email provides encryption, authentication, and secure communication, which are essential for protecting the confidentiality and integrity of email messages. This enhances email security and privacy, especially for sensitive and confidential emails.

Opportunistic TLS vs Forced TLS

While on the topic of TLS, we want to discuss its two types — opportunistic and forced TLS.

  • Opportunistic TLS: This version of TLS involves encrypting communication between two parties whenever possible, without strict requirements. In the context of email or web services, it means if both the sender and recipient support TLS encryption, they will use it to secure their communication. However, if one party doesn’t support TLS, the communication may continue without encryption.
  • Forced TLS: This is a stricter approach to email or web security compared to Opportunistic TLS. When using forced TLS, one party, typically the sender or server, mandates using TLS encryption for communication, and the other party must comply. If the recipient’s server doesn’t support TLS, it rejects the communication until a secure connection can be established.

This table highlights the differences between the two:

FeatureOpportunistic TLSForced TLS
EncryptionOptional: Encrypts when both sender and recipient support TLS.Mandatory: Requires encryption for all communication.
Security leniencyLess strict, allowing unencrypted communication if the other party doesn’t support TLS.Strict, enforcing encryption as a prerequisite for communication.
CompatabilityCompatible with a broader range of email systems, as it doesn’t force encryption.May lead to issues if the recipient’s server doesn’t support TLS.
FlexibilityOffers flexibility for cases where immediate encryption isn’t possible.Provides consistent, high-level security but may lead to non-delivery if TLS isn’t supported.
Use casesSuitable for situations where universal encryption isn’t feasible or necessary.Ideal for secure environments or scenarios where strict security is essential.
Data protectionProvides encryption and security when supported, enhancing security while allowing for flexibility.Ensures strong encryption for all communication, offering higher security assurance.
Opportunistic TLS vs Forced TLS

While Forced TLS can seem like the obvious choice, deciding between Opportunistic TLS and Forced TLS depends on specific security requirements and the level of control and assurance needed for a particular email system.


S/MIME, which stands for “Secure/Multipurpose Internet Mail Extensions,” is a widely used email security protocol that provides cryptographic security for emails. Many email providers use S/MIME to ensure the confidentiality, integrity, and authenticity of email communications.

Here are the features (and benefits) of using S/MIME to protect your emails:

  1. Email encryption: S/MIME enables the encryption of your email messages and their attachments. This ensures your content is secure and only the intended recipient can access it, preventing eavesdropping by unauthorized parties.
  2. Digital signatures: S/MIME allows you to apply digital signatures to your email messages. These signatures verify your authenticity and confirm that no one tampered with the email during transit.
  3. Public Key Infrastructure (PKI): S/MIME relies on PKI technology, which involves the use of public and private keys for encryption and digital signatures. This means you have to use your private key to sign the message, and the recipient uses your public key to verify the signature.
  4. Compatibility: Various email clients support S/MIME, making it a widely adopted standard. It ensures users of different email services can send and receive secure emails if they both support S/MIME.
  5. Authentication: S/MIME provides a strong level of authentication, making it challenging for malicious actors to impersonate you or modify the content of your emails.

S/MIME is commonly used in business and corporate email environments, where data security and privacy are of utmost importance. It is an effective solution for safeguarding sensitive and confidential email communications.

PGP and OpenPGP

PGP (Pretty Good Privacy) and OpenPGP are related encryption standards and systems designed for securing email and data communications. 

While PGP has a proprietary history, OpenPGP ensures interoperability across a wide range of open-source implementations, with GnuPG being a prime example. OpenPGP has gained trust in the security community for its open, collaborative approach, making it the preferred choice for those seeking secure email and data communication without proprietary constraints.

Let’s learn more about both protocols in detail.

Pretty Good Privacy (PGP)

The founder of PGP, Phil Zimmermann, originally developed it in 1991 as a proprietary encryption software and protocol. It gained popularity in the early 90s as a security measure for files uploaded to Bulletin Board Systems. The protocol may have waned in popularity over the years but is still used for email encryption, file encryption, and digital signatures. It utilizes a combination of symmetric and asymmetric encryption, along with a web of trust model, to manage encryption keys.

PGP is not open source, which has raised concerns about the ability to inspect the code for vulnerabilities. Various companies have owned PGP since, including PGP Corporation, which Symantec acquired. Despite its proprietary origins, various open-source PGP-compatible tools and implementations were developed, allowing for broader compatibility.


OpenPGP is an open-source standard and ecosystem based on the principles of PGP but not tied to any single company or entity. It defines a series of open standards and interoperable implementations for secure email and data communication. 

The most well-known open-source implementation of OpenPGP is GnuPG (GNU Privacy Guard). OpenPGP promotes transparency, collaboration, and open-source development, making it widely adopted and trusted. OpenPGP allows users to secure email communications, files, and digital signatures in a more open and secure manner.

SMTPS, IMAP, and POP3: Secure Enough?

Many people wrongly assume SMTPS, IMAP, and POP3 are security protocols; they are not.

SMTPS, IMAP, and POP3 are fundamental email protocols that support the exchange of emails across the internet. However, these protocols do not inherently provide security mechanisms. SMTPS, though it incorporates a security layer through SSL or TLS encryption, doesn’t enforce encryption universally, leaving email transmission vulnerable without proper configuration. 

IMAP and POP3, which are primarily focused on message retrieval, lack built-in encryption, potentially exposing email content during transmission. It’s crucial for users and organizations to implement additional security measures, such as TLS for SMTP, to safeguard emails and ensure the confidentiality and integrity of their messages.

In short, you cannot solely rely on SMTPS, IMAP, and POP3 to ensure the security and privacy of emails, as essential as they are in the world of electronic communication.


Sender Policy Framework (SPF) is an important email security protocol because it helps prevent email spoofing and unauthorized use of your domain names. SPF achieves this by specifying which email servers may send emails on behalf of your domain — this prevents malicious individuals from using your legitimate domain name to send fraudulent or phishing emails. 

SPF is vital in ensuring your authenticity and reducing the likelihood of recipients receiving deceptive or harmful emails. By implementing SPF, you can protect your brand’s reputation, enhance email deliverability, and reduce the risk of your emails being falsely marked as spam.


DomainKeys Identified Mail (DKIM) is another security protocol that plays a key role in email authentication. DKIM adds an encrypted digital signature to your email messages, which the recipient’s email server verifies. This signature guarantees your email’s content was secure during transit and that it indeed originates from your domain. 

DKIM helps prevent email forgery, phishing attacks, and unauthorized modifications to your email content. It enhances email trust and security by allowing recipients to confirm your authenticity, bolstering the integrity of email communications. 

This verification process is particularly important for your subscribers, as it helps protect them against malicious and fraudulent emails.


Domain-based Message Authentication, Reporting, and Conformance, or DMARC, is a protocol that prevents email spoofing and phishing attacks. DMARC allows you to specify an authentication process and define instructions to a server on how to handle emails if they fail authentication checks. This specification can include rejecting, quarantining, or delivering the email as usual. 

DMARC also provides reporting mechanisms that enable you to receive feedback about emails that pass or fail authentication, helping you monitor and improve your email security.

DMARC is essential because it enhances the overall security of email communications, protects your brand reputation, and builds trust with recipients. By implementing DMARC policies, you can reduce the risk of cybercriminals using your domain names for malicious purposes, thereby ensuring your emails are more secure, authentic, and reliable.


BIMI, or Brand Indicators for Message Identification, works in tandem with SPF, DKIM, and DMARC and lets you associate your brand logo with your email authentication records

To use BIMI, you have to publish a new DNS record that includes a URL to your logo. When your emails reach a server, the ESP verifies this association. Once it confirms the email is legitimate, mailbox providers can then display your logo next to the email in the recipient’s inbox. 

This security measure is great for branding plus it assures your readers that no one has spoofed your emails. Note that, in the near future, as BIMI gets more strict, you will need a VMC (Verified Mark Certificate) to prove you own the logo you are using for BIMI.

Teamwork: How SPF, DKIM, and DMARC Fight Spoofing and Phishing

SPF, DKIM, and DMARC work together to create a layered approach to email security and authentication. While SPF defines authorized sending servers, DKIM adds a digital signature to verify email integrity and authenticity, and finally, DMARC allows you to specify how to handle emails that fail these checks and provides feedback to improve your email security. 

By using all three in combination, you can significantly enhance the security and trustworthiness of your emails. BIMI will be joining this trio soon, which is especially important for big brands and those keen on protecting their brand identity, so you might as well get BIMI-compliant soon.

Campaign Refinery: A Secure Fortress

At Campaign Refinery, we believe email security is a top priority. As an email platform, we care about email recipients — we don’t like spam, and we don’t want spam emails going out from our servers either. This is why we have a rigid system to shortlist our clients, onboarding only those who share the same values as us. 

Here are a few of the features that demonstrate our commitment to ensuring email security:

  1. We insist our clients have SSL on their respective domains. This is great for brand credibility and also has a positive effect on your sender reputation.
  2. By only working with the best customers, we ensure our platform enjoys an excellent reputation with email service providers or ESPs.
  3. We require all our clients to implement SPF, DKIM, and DMARC on their domains — this three-pronged measure has done wonders for our clients’ sender reputation.
  4. We also automatically provision SSL/TLS on the tracking links inside emails sent using Campaign Refinery. Thanks to this step, recipients who click links in an email do not see any insecure content warnings, which can create a bad impression.

Staying proactive and informed about email security measures is essential to maintaining a secure and trusted online presence, especially in the world of email marketing. By implementing the protocols above and adhering to best practices, you can strengthen your email security and ensure the confidentiality, integrity, and authenticity of your messages.

Until next time — happy emailing!

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