Email is still one of the most common ways information moves across the Defense Industrial Base. It is also one of the easiest ways sensitive data gets exposed. For manufacturers and defense contractors handling CUI, email security is no longer just an IT concern. It is part of your CMMC compliance story.

As CMMC requirements continue to affect DoD contracts, email encryption and secure email practices are becoming areas assessors pay closer attention to. Understanding how email fits into CMMC expectations can help organizations avoid unnecessary risk and last minute fixes.

Most cyber incidents do not start with advanced attacks. They start with email. Phishing, spoofing, and accidental data sharing continue to be some of the most common causes of data exposure across the DIB.

CMMC focuses on protecting sensitive information wherever it exists and wherever it moves. That includes email. If your organization sends or receives CUI through email, you are expected to have controls in place to protect it from unauthorized access.

Saying “we try not to email CUI” is not enough on its own. Assessors want to see how email is actually handled, controlled, and monitored in practice.

Email encryption is simply a way to make sure the contents of an email cannot be read by anyone other than the intended recipient. If an email is intercepted, forwarded, or accessed improperly, the information remains unreadable.

From a compliance perspective, two areas matter most:

• Encryption while email is being sent

• Protection of emails once they are stored in mailboxes

Both play a role in reducing risk and supporting CMMC Level 2 expectations for protecting CUI.

CMMC does not tell organizations which email tool or encryption product to use. What it does require is protecting CUI in transit and controlling access to systems that store or transmit sensitive data.

In practical terms, that usually means:

• Emails containing CUI are encrypted automatically

• Access to email systems is limited and monitored

• There is visibility into who is sending and receiving sensitive information

Encryption on its own is not enough. It needs to be supported by clear policies, user training, and consistent enforcement.

Organizations preparing for CMMC often take a layered approach to email security. That may include automatic encryption rules, secure email gateways, multi factor authentication, and basic data loss prevention controls.

Just as important is documenting how these controls are used and training employees on when and how to handle sensitive information. Assessors are looking for consistency, not perfection.

One of the most common misunderstandings about CMMC is that installing a tool equals compliance. In reality, CMMC is about whether controls are implemented, documented, and followed over time.

Email encryption works best when it is part of a broader process that includes policies, training, and oversight. Organizations that take this approach are far better positioned during an assessment.

If you are a manufacturer or defense supplier, email security should be reviewed early in your CMMC planning. Waiting until the end often leads to rushed decisions and unnecessary costs.

Good questions to ask include:

• Where does CUI move through our email system?

• Is encryption automatic or dependent on user behavior?

• Can we show evidence that controls are in place and working?

• Do employees understand how to handle sensitive information?

Answering these questions early makes compliance easier and more defensible.

Email remains one of the most important and most overlooked areas of CMMC readiness. For Defense Industrial Base organizations, securing email is not just about passing an assessment. It is about protecting sensitive data, maintaining trust, and staying eligible for DoD work.

Organizations that address email encryption and security as part of their overall CMMC strategy tend to move faster, reduce rework, and avoid unnecessary risk later.