Guidelines for the Generation of Message IDs and Similar Unique Identifiers

Document Type Expired Internet-Draft (usefor WG)
Last updated 1998-09-02
Stream IETF
Intended RFC status (None)
Expired & archived
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Stream WG state WG Document
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IESG IESG state Expired
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


[RFC822] and [RFC1036] define so-called 'Message-IDs' that represent a unique identifier for email and netnews messages. A similar identifier is also used by [RFC2045] for the 'Content-ID' label. For each of these protocols, uniqueness of the identifiers generated is more or less essential. Unfortunately, the original Message-ID specification requires that the generator have an own, non-temporary full qualified domain name available, which does not allow hosts that are connected via dialup lines and get dynamically assigned IP addresses (and hostnames) to generate unique IDs offline. This memo provides recommendations for the generation of such IDs without risking non-uniqueness.


Claus Faerber (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)