XEP-0157: Contact Addresses for XMPP Services

This document defines a method for specifying contact addresses related to an XMPP service.

NOTICE: This document is currently within Last Call or under consideration by the XMPP Council for advancement to the next stage in the XSF standards process.

Document Information

Series: XEP
Number: 0157
Publisher: XMPP Standards Foundation
Status: Proposed
Type: Informational
Version: 0.5
Last Updated: 2007-01-06
Approving Body: XMPP Council
Dependencies: XMPP Core
Supersedes: None
Superseded By: None
Short Name: N/A
Wiki Page: <http://wiki.jabber.org/index.php/Contact Addresses for XMPP Services (XEP-0157)>

Author Information

Peter Saint-Andre

Email: stpeter@jabber.org
JID: stpeter@jabber.org

Jacek Konieczny

Email: jajcus@jajcus.net
JID: jajcus@jabber.bnet.pl

Legal Notice

This XMPP Extension Protocol is copyright 1999 - 2007 by the XMPP Standards Foundation (XSF) and is in full conformance with the XSF's Intellectual Property Rights Policy <http://www.xmpp.org/extensions/ipr-policy.shtml>. This material may be distributed only subject to the terms and conditions set forth in the Creative Commons Attribution License (<http://creativecommons.org/licenses/by/2.5/>).

Discussion Venue

The preferred venue for discussion of this document is the Standards discussion list: <http://mail.jabber.org/mailman/listinfo/standards>.

Relation to XMPP

The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 3920) and XMPP IM (RFC 3921) specifications contributed by the XMPP Standards Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this document has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.

Conformance Terms

The following keywords as used in this document are to be interpreted as described in RFC 2119: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".

Table of Contents

1. Introduction
2. Email Address
3. XMPP Address
4. Deployment Notes
5. Security Considerations
6. IANA Considerations
7. XMPP Registrar Considerations
Revision History

1. Introduction

Note: This document describes a protocol or best practice that is intended for incorporation into the specification that will supersede RFC 3920 [1] within the Internet Standards Process, i.e., rfc3920bis [2]. This document is provided only for the purpose of open community discussion of the potential modification and will be obsoleted as soon as the relevant RFC is published.

RFC 2142 [3] specifies conventional electronic mailbox names for common services, roles, and functions related to SMTP, NNTP, and HTTP (such as postmaster@domain.tld, usenet@domain.tld, and webmaster@domain.tld). However, no such conventional email address or XMPP address (JID) has been specified for XMPP services. This document remedies that oversight.

2. Email Address

Consistent with RFC 2142, a domain that offers a Jabber/XMPP service SHOULD provide an Internet mailbox of "XMPP" for inquiries related to that service.

3. XMPP Address

Many existing Jabber/XMPP server implementations use the bare domain (<domain.tld>) of the server (e.g., "example.org") as an alias for the server administrators, such that a <message/> stanza addressed to that domain name is delivered to the JIDs of the server administrators. [4] Unfortunately, using the "domain.tld" address as a way to direct messages to the server administrators may result in overloading of the bare domain address (i.e., it may be desirable to send messages to the server's address without having those messages delivered to the server admins, for example if the server doubles as a Publish-Subscribe [5] service). Therefore, it is instead RECOMMENDED to support a reserved address of <xmpp@domain.tld> for this functionality.

In particular, it is RECOMMENDED for a service provider to handle XML stanzas with a 'to' address of <xmpp@domain.tld> as follows:

  1. For <message/> stanzas, deliver them to the administrators of the XMPP service.

  2. For <presence/> stanzas, ignore them.

  3. For <iq/> stanzas, respond with a <service-unavailable/> error.

A service provider MAY aggregate presence from the server administrators so that the presence associated with <xmpp@domain.tld> reflects the presence of the server administrators (e.g., if at least one of the server administrators is online, then the alias <xmpp@domain.tld> will also appear to be online); alternatively, the service provider MAY refuse all requests for presence information about the <xmpp@domain.tld> address.

4. Deployment Notes

The "domain.tld" at which the XMPP service is hosted need not be the same as the "domain.tld" at which the email service is hosted. For example, it is common for a service provider to host its XMPP service at a hostname such as "jabber.example.org" whereas email related to the service provider is sent to a hostname of "example.org". Thus while the XMPP address and email address may be the same for some service providers (e.g., both "xmpp@example.com"), that similarity is not necessary.

Although some service providers that use the same address for both XMPP and email messaging may integrate delivery of messages sent by those mechanisms (e.g., XMPP messages sent while a user is offline are redirected to email delivery), XMPP and email remain separate messaging systems.

A service provider that supports the functionality specified herein may advertise the service through an XMPP URI (see RFC 4622 [6]) of <xmpp:xmpp@domain.tld> or (per XMPP URI Query Components [7]) <xmpp:xmpp@domain.tld?message>, and through a Mailto URI (see RFC 2368 [8]) of <mailto:xmpp@domain.tld>.

5. Security Considerations

Providing or advertising contact addresses may open those addresses to unwanted communication. Server administrators should balance the need for openness with the desire for control over communication with customers and peers.

6. IANA Considerations

This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [9].

7. XMPP Registrar Considerations

This document requires no interaction with the XMPP Registrar [10].


1. RFC 3920: Extensible Messaging and Presence Protocol (XMPP): Core <http://www.ietf.org/rfc/rfc3920.txt>.

2. rfc3921bis: proposed revisions to Extensible Messaging and Presence Protocol (XMPP): Core <http://www.ietf.org/internet-drafts/draft-saintandre-rfc3920bis-00.txt>. (work in progress)

3. RFC 2142: Mailbox Names for Common Services, Roles and Functions <http://www.ietf.org/rfc/rfc2142.txt>.

4. Currently, this functionality does not apply to <iq/> or <presence/> stanzas.

5. XEP-0060: Publish-Subscribe <http://www.xmpp.org/extensions/xep-0060.html>.

6. RFC 4622: Internationalized Resource Identifiers (IRIs) and Uniform Resource Identifiers (URIs) for the Extensible Messaging and Presence Protocol (XMPP) <http://www.ietf.org/rfc/rfc4622.txt>.

7. XEP-0147: XMPP URI Query Components <http://www.xmpp.org/extensions/xep-0147.html>.

8. RFC 2368: The mailto URL scheme <http://www.ietf.org/rfc/rfc2368.txt>.

9. The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>.

10. The XMPP Registrar maintains a list of reserved protocol namespaces as well as registries of parameters used in the context of XMPP extension protocols approved by the XMPP Standards Foundation. For further information, see <http://www.xmpp.org/registrar/>.

Revision History

Version 0.5 (2007-01-06)

Changed XMPP address from domain.tld/admin to xmpp@domain.tld.


Version 0.4 (2007-01-05)

Changed XMPP address from domain.tld to domain.tld/admin to prevent overloading.


Version 0.3 (2006-07-31)

Recommended support for RFC2142-style mailbox in addition to XMPP address.


Version 0.2 (2006-07-18)

Removed extended addressing recommendations pending further review.


Version 0.1 (2005-09-08)

Initial version.


Version 0.0.2 (2005-09-06)

Added security considerations and XMPP Registrar considerations.


Version 0.0.1 (2005-08-27)

First draft.