Does the SSL certificate type on my mail server impact email deliverability?

No, the specific type of SSL certificate (DV, OV, or EV) used for your mail server or website does not directly affect email deliverability. Mailbox providers primarily look for the presence of TLS encryption to ensure secure communication, not the level of organizational validation.

What kind of SSL/TLS is important for email?

For email, the crucial aspect is the use of TLS encryption during email transmission. This protects the data in transit. Separately, for links within your email, it's essential to use HTTPS to ensure security and improve how Mailbox Providers perceive your links. You can read more about TLS and email deliverability .

Will an EV certificate on my website improve my email deliverability?

While an EV certificate indicates a high level of organizational validation for a website, this validation is primarily for human users interacting with the site. Mailbox providers do not factor this into their email deliverability algorithms, which focus on email authentication protocols (SPF, DKIM, DMARC) and sender reputation.

Should I use HTTP links in my emails if my site has an SSL certificate?

No, it is generally not recommended to include HTTP links in your emails. Mailbox providers prefer and increasingly expect secure (HTTPS) links. Using HTTP links can raise red flags with spam filters and potentially lead to your emails being flagged as suspicious, negatively impacting your deliverability.

What are the most important factors for email deliverability?

Key factors include correctly configured email authentication (SPF, DKIM, DMARC) , a strong sender reputation (based on engagement, low complaints, and bounces), and using TLS for email transport. Content quality and list hygiene are also critical.

Does SSL certificate type affect email deliverability? - Sender reputation - Email deliverability - Knowledge base

When we talk about email deliverability, many technical aspects come into play, from DNS records to content quality. One question that often arises is about SSL certificates. Most people associate SSL with website security, ensuring that data exchanged between a browser and a server is encrypted and secure. But what about email? Specifically, does the type of SSL certificate you use have any bearing on whether your emails land in the inbox or the spam folder?

It's a common misconception that a more rigorously validated SSL certificate, like an Extended Validation (EV) certificate, might somehow signal greater trustworthiness to an Email Service Provider (ESP) or Mailbox Provider (MP), thereby improving deliverability. However, the reality of how email systems interact with SSL/TLS (Transport Layer Security, the successor to SSL) is quite different. Let's delve into the nuances of SSL certificate types and their actual impact on your email campaigns.

Understanding SSL certificate types

Before we dive into the specifics of email, it's helpful to understand the different types of SSL certificates commonly available for websites and other online services. These categories reflect varying levels of validation performed by Certificate Authorities (CAs).

Domain validation (DV) certificates

A Domain Validation certificate is the most basic and common type. To obtain one, you only need to prove that you control the domain name. This process is typically automated and can be completed quickly, often within minutes. Many hosting providers and services offer free DV certificates, such as those provided by Let's Encrypt.

Organization validation (OV) certificates

With an Organization Validation certificate, the CA verifies not only domain ownership but also the legitimacy of the organization applying for the certificate. This involves a more thorough manual vetting process, including checking business registration documents. OV certificates display organization details within the certificate, providing a higher level of trust than DV certificates.

Extended validation (EV) certificates

Extended Validation certificates offer the highest level of trust and require the most extensive verification. CAs conduct a rigorous vetting process, confirming the organization's legal, physical, and operational existence. This includes verifying business identity, physical address, and telephone number, often involving direct callbacks and official documentation. Historically, EV certificates would display the organization's name prominently in the browser's address bar, though this visual cue has largely been phased out by modern browsers. You can learn more about these types of certificates on the SSL Dragon blog.

Certificate type	Validation level	Cost	Typical use
Domain validation (DV)	Proves domain ownership.	Free to low cost.	Blogs, small businesses, internal sites.
Organization validation (OV)	Verifies domain ownership and organization's legitimacy.	Moderate cost.	Corporate websites, e-commerce sites.
Extended validation (EV)	Highest level of verification, confirming legal and physical existence.	High cost.	Financial institutions, major e-commerce platforms.

SSL and email encryption (TLS)

For email deliverability, what truly matters is the presence of encryption (TLS), not the specific type of SSL certificate used for your mail server. Mailbox providers prioritize the security of the connection to prevent eavesdropping and tampering. If your mail server supports and uses TLS, emails are encrypted in transit. This is a fundamental security practice that most modern email systems expect.

SSL certificates, or more accurately TLS certificates, enable this secure communication channel. When an email server connects to another, it establishes a TLS encrypted connection. The certificate primarily verifies the identity of the server and allows for the encryption handshake. The specific level of vetting (DV, OV, or EV) behind that certificate type has no bearing on how Mailbox Providers like

Google or

Yahoo process your email for deliverability purposes.

The key takeaway here is that an unencrypted connection is a red flag, but the type of validation doesn't add an extra layer of deliverability benefit. DigiCert explains that most cloud-based email providers use TLS/SSL encryption. Organizations can also install a TLS/SSL certificate to protect private email servers. Mailbox providers are primarily concerned with whether the connection is encrypted (TLS), not the specific type of certificate that enables it.

Ensure TLS is enabled

The primary focus for email deliverability concerning SSL/TLS should be ensuring your mail server is configured to use opportunistic TLS encryption for all outgoing mail. This ensures your emails are encrypted in transit whenever the receiving server supports it. You can review how

Google Workspace handles secure TLS connections. This is a direct deliverability factor.

Website SSL vs. email deliverability

While the type of SSL certificate on your mail server doesn't impact deliverability, the use of SSL/TLS for links within your emails can indirectly affect how your messages are perceived. If your email contains links, especially to your website or tracking domains, those links should use HTTPS. Modern Mailbox Providers and spam filters prefer, and sometimes even require, secure links. Unsecured (HTTP) links can trigger warnings or even cause emails to be flagged as suspicious, hurting your sender reputation. For more on this, read about SSL for tracked links and images.

The trust conveyed by an OV or EV certificate is primarily for human users visiting a website, not for automated email systems. Mailbox providers don't typically inspect the certificate type of linked domains to determine deliverability. Their algorithms focus on the protocol (HTTPS vs. HTTP) and the reputation of the linked domain itself. Therefore, investing in a more expensive OV or EV certificate for your website in hopes of boosting email deliverability is unlikely to yield results.

It's also worth noting that the general shift towards pervasive encryption online means that having any valid SSL certificate on your web assets is now standard practice and expected. A website without HTTPS can hurt your overall brand perception and indirectly impact trust, but it's not the SSL certificate *type* that email systems care about.

Website SSL certificate type

Mailbox providers do not actively check the validation level (DV, OV, EV) of SSL certificates on linked websites or tracking domains to determine email deliverability or sender reputation. Their focus is on the security of the transport layer and the reputation of your sending infrastructure.

Email authentication and content

What Mailbox Providers do care about are your email authentication records (SPF, DKIM, DMARC), your sender reputation, bounce rates, spam complaints, and overall engagement signals. They also look for secure links (HTTPS) within your emails. This is directly relevant to email deliverability and sender reputation.

What truly impacts email deliverability?

Instead of focusing on the type of SSL certificate, attention should be directed to the foundational elements of email authentication and sender reputation. These are the true determinants of whether your emails reliably reach the inbox.

Email authentication: Implement and maintain strong SPF, DKIM, and DMARC records. These protocols verify that your emails are legitimate and prevent spoofing. Mailbox providers heavily rely on these to filter out malicious or unwanted mail.
Sender reputation: Your sending domain and IP address reputation are paramount. Factors like low bounce rates, minimal spam complaints, and high engagement (opens, clicks, replies) signal trustworthiness to Mailbox Providers. Conversely, being listed on an email blacklist (or blocklist) can severely impact your deliverability. For insights into this, read our guide to how email blacklists work.
Content quality: Avoid spammy language, excessive capitalization, and broken links. Personalize your messages and provide value to your recipients.
List hygiene: Regularly clean your email lists to remove inactive or invalid addresses, reducing bounce rates and protecting your sender reputation.

Mailbox providers are sophisticated and use a holistic approach to evaluate incoming email. Their systems prioritize the security of the connection and the authenticity of the sender above the specific validation level of a certificate. What matters is that your emails are authenticated and sent over an encrypted channel. For more information about the security provided by certificates, Kaspersky provides a helpful definition of an SSL certificate.

Focusing on these core elements will yield far greater improvements in your email deliverability than debating the merits of different SSL certificate types for your mail server or website. Having secure links in your emails by using HTTPS is also a good practice, as Mailbox Providers increasingly favor it.

Views from the trenches

Best practices

Always ensure your mail server is configured for opportunistic TLS encryption.

Prioritize robust email authentication with SPF, DKIM, and DMARC.

Maintain a healthy sender reputation by monitoring engagement and complaint rates.

Use HTTPS for all links within your emails, including tracking domains.

Common pitfalls

Believing a higher-validation SSL certificate type (OV/EV) for your website automatically boosts email deliverability.

Neglecting email authentication (SPF, DKIM, DMARC) in favor of web security measures.

Using HTTP links within emails, which can flag messages as suspicious by Mailbox Providers.

Ignoring sender reputation metrics like bounces and spam complaints.

Expert tips

Mailbox providers are primarily interested in the authentication of the email and how users respond to it. The specifics of an SSL certificate type do not factor into this.

EV certificates were largely a financial play, and their perceived benefits for trust have been largely superseded by the widespread availability of free DV certificates for general web encryption.

While web-based SSL certificate types don't impact email deliverability, the concept of verifying an organization's brand for email is seen in BIMI (Brand Indicators for Message Identification).

There's certainly a lot of incredibly annoying interaction with a certificate authority for higher-level certificates, which many have mostly managed to block out of memory.

Expert view

Expert from Email Geeks says that the type of SSL certificate used for a sending domain has no impact on email deliverability whatsoever. Mailbox providers are mainly interested in mail authentication and user engagement.

2024-01-12 - Email Geeks

Expert view

Expert from Email Geeks notes that while links in messages are used to fingerprint content, and HTTP versus HTTPS might have a small effect, anything beyond that, regarding SSL certificate details, does not affect deliverability.

2024-01-12 - Email Geeks

Prioritizing the right security for email

Ultimately, the type of SSL certificate you choose for your website or server (DV, OV, or EV) does not directly affect email deliverability. Mailbox providers do not differentiate between these certificate types when assessing your email's legitimacy or trustworthiness. What they care about is the presence of encryption (TLS) for secure email transport and the overall health of your sending reputation, which is built on factors like email authentication (SPF, DKIM, DMARC), consistent sending practices, and positive recipient engagement.