Message-ID
Learn what a Message-ID is, how it uniquely identifies emails, and how DMARCeye uses it to analyze and track message authentication.
What is a Message-ID in email?
The Message-ID is a unique identifier assigned to every email message, defined by RFC 5322. It appears in the message headers and ensures that each email can be uniquely referenced, tracked, or threaded throughout its lifecycle. The Message-ID is critical for preventing duplication, managing conversations, and identifying messages during delivery or authentication analysis.
Each Message-ID must be globally unique. It is typically generated automatically by the sending mail server or client when the message is created, following a format that includes random or timestamped elements and the sender’s domain.
Message-ID Format
The standard syntax looks like this:
Message-ID: <abc123xyz@example.com>Everything inside the angle brackets (“< >”) constitutes the identifier. The part after the “@” symbol usually matches the domain that generated the message, which helps link the ID to its origin.
Functions of the Message-ID
- Identifies messages across mail systems and servers
- Supports threading in email clients (Reply, Forward, etc.)
- Prevents message duplication during forwarding or retransmission
- Helps analysts trace or debug message delivery paths
In addition, Message-IDs assist in verifying the authenticity of messages in forensic or DMARC report analysis, as each ID can be linked to a specific sending source and timestamp.
Common Issues
Some poorly configured mail servers reuse or omit Message-IDs, which can cause delivery problems, spam classification, or analysis inconsistencies. Missing or duplicate IDs may trigger filtering by mailbox providers.
Message-ID and DMARCeye
DMARCeye uses Message-IDs to correlate authentication outcomes and detect unusual sending patterns. By mapping unique identifiers across multiple reports, the platform distinguishes legitimate messages from spoofed or mass-sent duplicates.
This capability enhances forensic tracking, ensuring each message can be traced accurately across its delivery path for authentication and compliance verification.
- AI-powered monitoring, analysis, and troubleshooting recommendations
- Smart and configurable alerts
- Overview dashboard makes managing multiple domains simple
- Affordable, per-domain pricing make it easy to scale
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.