Messid

Messid, short for message identifier, is a term used in computing to denote a unique identifier assigned to a specific message within a system. It is used in email, messaging applications, event streams, and databases to enable retrieval, deduplication, threading, and cross-referencing.

Messids vary in format and scope. They can be globally unique across a service or limited to a mailbox, chat room, or topic. Common forms include numeric counters, universally unique identifiers (UUIDs/GUIDs), or structured strings that embed a timestamp or origin. The choice influences performance, privacy, and resilience to failures or clock skew.

In practice, messids appear in many contexts. In email, the Message-ID header is the canonical messid, such as Message-ID: <[email protected]>. In other systems, IDs may be generated by servers or clients and are typically opaque to users. In chat and collaboration tools, messids enable message threading and stable references across devices; in log aggregation, they help correlate events from the same source.

Generation and lifecycle: Messids are typically created at message creation, persisted with the payload, and remain invariant for the message’s lifetime. They may be included in archives and index entries and are sometimes deleted only under privacy or data-retention policies.

See also: message ID, threading ID, correlation ID, deduplication. Privacy and security considerations: avoid exposing predictable sequences; use strong randomness or UUIDs when appropriate.