BCC (Blind Carbon Copy)

What is BCC (Blind Carbon Copy)?

BCC, or Blind Carbon Copy, is an email header field that allows a sender to include additional recipients in a message without revealing their addresses to others. Unlike the “To” and “CC” fields, which display all listed recipients, the BCC field keeps its entries hidden, providing privacy and discretion in communication.

BCC is widely used for confidential messaging, internal updates, or bulk distribution where recipient anonymity is required. While essential for convenience, it also poses potential security and compliance challenges if misused.

How BCC Works

When an email is composed, the sender may include multiple addresses in the BCC field. During transmission, the SMTP protocol processes these addresses separately from the “To” and “CC” fields. The message is delivered to all intended recipients, but BCC addresses are stripped from the visible message headers before delivery.

Example email header:

In this case, only “marketing@example.com” and “info@example.org” will appear in the visible headers. The BCC recipient (“ceo@example.com”) receives the message without their address being disclosed.

Security and Privacy Considerations

• Protects recipients’ privacy during mass communication
• Prevents email address exposure to unauthorized users
• Can be misused for spam or stealth communications
• May complicate forensic analysis or message tracing if abused

From a security perspective, improper use of BCC can obscure visibility during email investigations. Organizations should implement logging and monitoring to track hidden recipients when necessary.

BCC and Email Authentication

Although the BCC field does not directly affect DMARC, SPF, or DKIM validation, it plays a role in understanding message routing and trust. Hidden recipients can create confusion in incident response or compliance audits if the message source is compromised or spoofed.

BCC and DMARCeye

DMARCeye analyzes email headers, including those that show message distribution patterns, to help detect anomalies or unusual recipient behavior. While BCC fields are not visible in standard reports, DMARCeye uses forensic insight from authentication data to identify suspicious routing activity or unexpected message forwarding.

This analysis strengthens visibility across mail flows, even when certain recipients are hidden, maintaining consistent protection and transparency across all communications.

Sign up for a free trial of DMARCeye today and secure your email domain.

To learn more about DMARC and DMARC-related terms, explore the DMARCeye Glossary.