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How an Email Certificate Works and Why It’s Necessary for Security

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An overview of how an email encryption certificate provides secure email communication

When you send an email through conventional email platforms such as Outlook, Gmail, or Yahoo, the information could be visible to people who know how to look. Emails are bounced around through a series of servers and across the internet. As such, they’re not secure without having encryption or other protective mechanisms in place. This means that they can be “read” by hackers, putting your company’s (and customers’) sensitive data at risk. This not only opens your company up to the financial and reputational costs associated with a data breach, but to exorbitant regulatory fines due to noncompliance as well.

So, how can you secure email communication in a time when phishing and data breaches are on the rise? Let’s break down how email certificates work and why they’re needed to ensure your emails are secure.

What is an Email Certificate?

An email certificate is a digital file that is installed to your email application to enable secure email communication. These certificates are known by many names — email security certificates, email encryption certificates, S/MIME certificates, etc. S/MIME, which stands for “secure/multipurpose internet mail extension,” is a certificate that allows users to digitally sign their email communications as well as encrypt the content and attachments included in them. Not only does this authenticate the identity of the sender to the recipient, but it also protects the integrity of the email data before it is transmitted across the internet.

How an Email Security Certificate Works

In a nutshell, an S/MIME email certificate allows you to:

  • Encrypt your emails so that only your intended recipient can access the content of the message.
  • Digitally sign your emails so the recipient can verify that the email was, in fact, sent by you and not a phisher posing as you.

The way that an email encryption certificate works is by using asymmetric encryption. It uses a public key to encrypt the email and send it so that the recipient, who has the matching private key, can decrypt the entire message (and any attachments) automatically. Asymmetric encryption is also what’s behind the SSL/TLS protocol as well as cryptocurrencies.

Let’s say that you need to send an email to a colleague about company financial data. Here is an email of how this process works when sending the email without and with an email certificate:

Without an S/MIME Email Certificate InstalledWith an S/MIME Email Certificate Installed
• You create a new email in Outlook.

• You draft the content of the email and attach an Excel spreadsheet.

• You hit “Send” to send the plaintext email from Outlook.

• The email is sent from your email platform to the email server via an unencrypted channel.

• The email content (and the spreadsheet attachment) are sent from the email server to the internet.

• The email data is then sent from the internet to the recipient’s email server.

• The recipient receives an unsigned, unencrypted email from you, an unverified sender. They open the email and read its plaintext message and access its plaintext Excel spreadsheet.
• You create a new email in Outlook.

• You draft the content of the email and attach an Excel spreadsheet.

• You hit “Send” to send the plaintext email from Outlook.

• Before the message leaves Outlook, the S/MIME email certificate automatically:

1. digitally signs the email to verify your identity as the sender.

2. encrypts the plaintext email data using asymmetric encryption (a public key).

• The secure, encrypted email moves from your email platform to the server via an unencrypted channel.

• The encrypted email content and attachment are sent from the email server to the internet.

• The email data is then sent from the internet to the recipient’s email server.

• The recipient receives the encrypted email, which is digitally signed to verify your identity as the sender.

• When they open the email, the private key automatically decrypts the content and email attachment so they can read it in plaintext.

Did you notice a difference in the two scenarios? That’s why an email certificate is so important. In the first scenario that lacks an email encryption certificate, the sender sends a plaintext, unencrypted email to the recipient via an unencrypted server and the internet. This leaves the message and its attachments vulnerable to interception by hackers who can “read” the data and translate it to plaintext. In the second scenario in which the sender uses an email security certificate, the sender writes a plaintext email that is encrypted prior to moving to the unencrypted server and the internet. This means that even if the hacker managed to intercept the message, they would be unable to decrypt the data because they wouldn’t have the private key. Even once the email reaches the recipient, it remains encrypted while it’s sitting on their computer. This email encryption process helps to protect your data both when it is at rest and in transit.

Why Email Security Certificates Are Vital to Secure Email Communication

Email encryption certificate is the digital certificate used to sign the email to ensure the receiver that the email has come from a legitimate person and also that the email has not been tampered with while in transit. The email is encrypted with Public Key Infrastructure (PKI) algorithm while in transit so that only the intended recipient can read it.

Email Security Helps to Protect Your Business and Build Customer Trust

As we mentioned earlier, phishing attacks are on the rise and are now the leading cause of cyber attacks. A simple email can wreak havoc on a company of any size by providing a hacker with access to their systems — including financial information, proprietary designs, client information, and data backups — and, ultimately, could cause the company to permanently close its doors.

To help keep their business’s email communications secure, companies can consider the different ways that they can choose to secure their emails — anti-spam filters and plugins, Domain Keys Identified Mail (DKIM), sender policy framework (SPF), encrypting email servers, etc. While using a multi-layered approach is both advisable and necessary, using S/MIME email certificates is among the most important methods. After all, a digital certificate for email encryption enables you to encrypt the contents of an email before it ever leaves your email account.

Email Security Helps to Prevent Noncompliance

An additional benefit of using an email certificate is that it can help your organization with regulatory compliance. Regulations such as the Payment Card Industry’s Data Security Standard (PCI-DSS), the European Union’s General Data Protection Regulation (GDPR) data security requirements, and the Healthcare Insurance Portability and Accountability Act (HIPAA) underscore the importance of having encryption and other protection mechanisms in place for sending sensitive data via email and other electronic methods.

Final Thoughts

Now you know how you can secure your email communications using an email certificate from a reputable certificate authority. We hope that we’ve answered your questions about how an email certificate works and why using one is so important — both for your organization and your customers. 

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