| Internet-Draft | Use of SMTPUTF8 Addresses in EPP | September 2024 |
| Belyavskiy, et al. | Expires 3 April 2025 | [Page] |
The Extensible Provisioning Protocol (EPP) does not natively support internationalized email addresses because the specifications for these addresses did not exist when EPP was developed. This document describes a command-response extension that adds support for associating either an internationalized email address or a second all-ASCII address with an EPP contact object and specifies how these addresses can be used by EPP clients and servers.¶
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The framework for internationalized email addresses is described in [RFC6530]. This document describes an Extensible Provisioning Protocol (EPP) [RFC5730] command-response extension that adds support for adding a second email address to the EPP contact object [RFC5733] mapping. As described in [RFC5733], the email address associated with the base contact object MUST be an ASCII-only address. The second email address can be either an ASCII-only email address or an internationalized, SMTPUTF8 [RFC6530] email address. This second address can be used to identify an alternate ASCII-only email address for use in case of primary address delivery issues. It can also be used to identify an SMTPUTF8 address for contact purposes, in which case the ASCII-only address can be used in case of SMTPUTF8 address delivery issues.¶
While this extension adds support for an additional email address to contact objects, and that additional email address can be an SMTPUTF8 address, it does not in any way update or change any other EPP extension that includes an email address. Adding support for SMTPUTF8 addresses to those extensions will require an update to the relevant extension specifications.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
XML is case sensitive. Unless stated otherwise, XML specifications and examples provided in this document MUST be interpreted in the character case presented in order to develop a conforming implementation.¶
In examples, "C:" represents lines sent by a protocol client and "S:" represents lines returned by a protocol server. Indentation and white space in the examples are provided only to illustrate element relationships and are not REQUIRED in the protocol.¶
The XML namespace prefix "addlEmail" is used for the namespace "urn:ietf:params:xml:ns:epp:addlEmail-1.0", but implementations MUST NOT depend on it and instead employ a proper namespace-aware XML parser and serializer to interpret and output the XML documents.¶
Servers that implement this extension SHOULD provide a way for clients to progressively update their implementations when a new version of the extension is deployed. A newer version of the extension is expected to use an XML namespace URI with a higher version number than earlier versions.¶
The EPP contact object mapping [RFC5733] normatively references [RFC5322] as the specification for email address syntax. That specification does not include support for internationalized email addresses. RFC 6530 [RFC6530] provides an overview and describes the framework for internationalized email. SMTPUTF8 email address syntax is described in Section 3.3 of [RFC6531]. [RFC6531] extends the Mailbox, Local-part and Domain ABNF rules in [RFC5321] to support "UTF8-non-ascii", defined in Section 3.1 of [RFC6532], for the local-part and U-label, defined in Section 2.3.2.1 of [RFC5890], for the domain. The validation rules described in RFC 6531 MUST be followed when processing internationalized email addresses associated with this extension.¶
A second email address can be set using the <addlEmail:addlEmail> element with the command and response extensions defined in Section 6. The <addlEmail:addlEmail> element contains the following child element:¶
The client and the server can signal support for the extension using a namespace URI in the login and greeting extension services respectively. The namespace URI "urn:ietf:params:xml:ns:epp:addlEmail-1.0" is used to signal support for the extension. The client includes the namespace URI in an <svcExtension> <extURI> element of the [RFC5730] <login> Command. The server includes the namespace URI in an <svcExtension> <extURI> element of the [RFC5730] greeting.¶
If both client and server have indicated support for SMTPUTF8 addresses during session establishment, they MUST be able to process an SMTPUTF8 address in any extended contact object during the established EPP session. Server and client obligations when this extension has been successfully negotiated in the EPP session are described below.¶
The server MUST satisfy the following obligations when support for this extension has been negotiated:¶
The client MUST satisfy the following obligations when support for this extension has been negotiated:¶
An extended contact object MUST NOT be provided or returned by either an EPP client or an EPP server when support for this extension is not successfully negotiated at the start of an EPP session.¶
A detailed description of the EPP syntax and semantics can be found in the EPP core protocol specification [RFC5730]. This section defines the provisioning of an alternate email address.¶
EPP provides three commands to retrieve object information: <check> to determine if an object can be provisioned, <info> to retrieve information associated with an object, and <transfer> to retrieve object-transfer status information.¶
This extension does not add any elements to the EPP <check> command or <check> response described in [RFC5730].¶
This extension does not add any elements to the EPP <info> command response described in [RFC5730].¶
If the query was successful, the server replies with an <addlEmail:addlEmail> element (Section 4) along with the regular EPP <resData>.¶
The following is an example <info> contact response using the <addlEmail:addlEmail> extension with no alternate email address:¶
S:<?xml version="1.0" encoding="UTF-8" standalone="no"?> S:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0"> S: <response> S: <result code="1000"> S: <msg>Command completed successfully</msg> S: </result> S: <resData> S: <contact:infData S: xmlns:contact="urn:ietf:params:xml:ns:contact-1.0"> S: <contact:id>sh8013</contact:id> S: <contact:roid>SH8013-REP</contact:roid> S: <contact:status s="linked"/> S: <contact:status s="clientDeleteProhibited"/> S: <contact:postalInfo type="int"> S: <contact:name>John Doe</contact:name> S: <contact:org>Example Inc.</contact:org> S: <contact:addr> S: <contact:street>123 Example Dr.</contact:street> S: <contact:street>Suite 100</contact:street> S: <contact:city>Dulles</contact:city> S: <contact:sp>VA</contact:sp> S: <contact:pc>20166-6503</contact:pc> S: <contact:cc>US</contact:cc> S: </contact:addr> S: </contact:postalInfo> S: <contact:voice x="1234">+1.7035555555</contact:voice> S: <contact:fax>+1.7035555556</contact:fax> S: <contact:email>[email protected]</contact:email> S: <contact:clID>ClientY</contact:clID> S: <contact:crID>ClientX</contact:crID> S: <contact:crDate>1999-04-03T22:00:00.0Z</contact:crDate> S: <contact:upID>ClientX</contact:upID> S: <contact:upDate>1999-12-03T09:00:00.0Z</contact:upDate> S: <contact:trDate>2000-04-08T09:00:00.0Z</contact:trDate> S: <contact:authInfo> S: <contact:pw>2fooBAR</contact:pw> S: </contact:authInfo> S: <contact:disclose flag="0"> S: <contact:voice/> S: <contact:email/> S: </contact:disclose> S: </contact:infData> S: </resData> S: <extension> S: <addlEmail:addlEmail S: xmlns:addlEmail="urn:ietf:params:xml:ns:epp:addlEmail-1.0"> S: <addlEmail:email/> S: </addlEmail:addlEmail> S: </extension> S: <trID> S: <clTRID>ABC-12345</clTRID> S: <svTRID>54322-XYZ</svTRID> S: </trID> S: </response> S:</epp>
The following is an example <info> contact response using the <addlEmail:addlEmail> extension with an ASCII alternate email address:¶
S:<?xml version="1.0" encoding="UTF-8" standalone="no"?> S:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0"> S: <response> S: <result code="1000"> S: <msg>Command completed successfully</msg> S: </result> S: <resData> S: <contact:infData S: xmlns:contact="urn:ietf:params:xml:ns:contact-1.0"> S: <contact:id>sh8013</contact:id> S: <contact:roid>SH8013-REP</contact:roid> S: <contact:status s="linked"/> S: <contact:status s="clientDeleteProhibited"/> S: <contact:postalInfo type="int"> S: <contact:name>John Doe</contact:name> S: <contact:org>Example Inc.</contact:org> S: <contact:addr> S: <contact:street>123 Example Dr.</contact:street> S: <contact:street>Suite 100</contact:street> S: <contact:city>Dulles</contact:city> S: <contact:sp>VA</contact:sp> S: <contact:pc>20166-6503</contact:pc> S: <contact:cc>US</contact:cc> S: </contact:addr> S: </contact:postalInfo> S: <contact:voice x="1234">+1.7035555555</contact:voice> S: <contact:fax>+1.7035555556</contact:fax> S: <contact:email>[email protected]</contact:email> S: <contact:clID>ClientY</contact:clID> S: <contact:crID>ClientX</contact:crID> S: <contact:crDate>1999-04-03T22:00:00.0Z</contact:crDate> S: <contact:upID>ClientX</contact:upID> S: <contact:upDate>1999-12-03T09:00:00.0Z</contact:upDate> S: <contact:trDate>2000-04-08T09:00:00.0Z</contact:trDate> S: <contact:authInfo> S: <contact:pw>2fooBAR</contact:pw> S: </contact:authInfo> S: <contact:disclose flag="0"> S: <contact:voice/> S: <contact:email/> S: </contact:disclose> S: </contact:infData> S: </resData> S: <extension> S: <addlEmail:addlEmail S: xmlns:addlEmail="urn:ietf:params:xml:ns:epp:addlEmail-1.0"> S: <addlEmail:email>[email protected]</addlEmail:email> S: </addlEmail:addlEmail> S: </extension> S: <trID> S: <clTRID>ABC-12345</clTRID> S: <svTRID>54322-XYZ</svTRID> S: </trID> S: </response> S:</epp>
The following is an example <info> contact response using the <addlEmail:addlEmail> extension with an SMTPUTF8 primary email address:¶
S:<?xml version="1.0" encoding="UTF-8" standalone="no"?> S:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0"> S: <response> S: <result code="1000"> S: <msg>Command completed successfully</msg> S: </result> S: <resData> S: <contact:infData S: xmlns:contact="urn:ietf:params:xml:ns:contact-1.0"> S: <contact:id>sh8013</contact:id> S: <contact:roid>SH8013-REP</contact:roid> S: <contact:status s="linked"/> S: <contact:status s="clientDeleteProhibited"/> S: <contact:postalInfo type="int"> S: <contact:name>John Doe</contact:name> S: <contact:org>Example Inc.</contact:org> S: <contact:addr> S: <contact:street>123 Example Dr.</contact:street> S: <contact:street>Suite 100</contact:street> S: <contact:city>Dulles</contact:city> S: <contact:sp>VA</contact:sp> S: <contact:pc>20166-6503</contact:pc> S: <contact:cc>US</contact:cc> S: </contact:addr> S: </contact:postalInfo> S: <contact:voice x="1234">+1.7035555555</contact:voice> S: <contact:fax>+1.7035555556</contact:fax> S: <contact:email>[email protected]</contact:email> S: <contact:clID>ClientY</contact:clID> S: <contact:crID>ClientX</contact:crID> S: <contact:crDate>1999-04-03T22:00:00.0Z</contact:crDate> S: <contact:upID>ClientX</contact:upID> S: <contact:upDate>1999-12-03T09:00:00.0Z</contact:upDate> S: <contact:trDate>2000-04-08T09:00:00.0Z</contact:trDate> S: <contact:authInfo> S: <contact:pw>2fooBAR</contact:pw> S: </contact:authInfo> S: <contact:disclose flag="0"> S: <contact:voice/> S: <contact:email/> S: </contact:disclose> S: </contact:infData> S: </resData> S: <extension> S: <addlEmail:addlEmail S: xmlns:addlEmail="urn:ietf:params:xml:ns:epp:addlEmail-1.0"> S: <addlEmail:email primary="true">麥克風@example.com</addlEmail:email> S: </addlEmail:addlEmail> S: </extension> S: <trID> S: <clTRID>ABC-12345</clTRID> S: <svTRID>54322-XYZ</svTRID> S: </trID> S: </response> S:</epp>
This extension does not add any elements to the EPP <transfer> query command or <transfer> query response described in [RFC5730].¶
EPP provides five commands to transform objects: <create> to create an instance of an object, <delete> to delete an instance of an object, <renew> to extend the validity period of an object, <transfer> to manage object sponsorship changes, and <update> to change information associated with an object.¶
This extension defines additional elements to extend the EPP <create> command of an object mapping like [RFC5733].¶
The EPP <create> command provides a transform operation that allows a client to create an instance of an object. In addition to the EPP command elements described in an object mapping like [RFC5733], the command MUST contain a child <addlEmail:addlEmail> element (Section 4) for the client to set an alternate email address.¶
The following is an example <create> command to create a contact object with an alternate ASCII email address:¶
C:<?xml version="1.0" encoding="UTF-8" standalone="no"?> C:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0"> C: <command> C: <create> C: <contact:create C: xmlns:contact="urn:ietf:params:xml:ns:contact-1.0"> C: <contact:id>sh8013</contact:id> C: <contact:postalInfo type="int"> C: <contact:name>John Doe</contact:name> C: <contact:org>Example Inc.</contact:org> C: <contact:addr> C: <contact:street>123 Example Dr.</contact:street> C: <contact:street>Suite 100</contact:street> C: <contact:city>Dulles</contact:city> C: <contact:sp>VA</contact:sp> C: <contact:pc>20166-6503</contact:pc> C: <contact:cc>US</contact:cc> C: </contact:addr> C: </contact:postalInfo> C: <contact:voice x="1234">+1.7035555555</contact:voice> C: <contact:fax>+1.7035555556</contact:fax> C: <contact:email>[email protected]</contact:email> C: <contact:authInfo> C: <contact:pw>2fooBAR</contact:pw> C: </contact:authInfo> C: <contact:disclose flag="0"> C: <contact:voice/> C: <contact:email/> C: </contact:disclose> C: </contact:create> C: </create> C: <extension> C: <addlEmail:addlEmail C: xmlns:addlEmail="urn:ietf:params:xml:ns:epp:addlEmail-1.0"> C: <addlEmail:email>[email protected]</addlEmail:email> C: </addlEmail:addlEmail> C: </extension> C: <clTRID>ABC-12345</clTRID> C: </command> C:</epp>
The following is an example <create> command to create a contact object with a primary SMTPUTF8 email address:¶
C:<?xml version="1.0" encoding="UTF-8" standalone="no"?> C:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0"> C: <command> C: <create> C: <contact:create C: xmlns:contact="urn:ietf:params:xml:ns:contact-1.0"> C: <contact:id>sh8013</contact:id> C: <contact:postalInfo type="int"> C: <contact:name>John Doe</contact:name> C: <contact:org>Example Inc.</contact:org> C: <contact:addr> C: <contact:street>123 Example Dr.</contact:street> C: <contact:street>Suite 100</contact:street> C: <contact:city>Dulles</contact:city> C: <contact:sp>VA</contact:sp> C: <contact:pc>20166-6503</contact:pc> C: <contact:cc>US</contact:cc> C: </contact:addr> C: </contact:postalInfo> C: <contact:voice x="1234">+1.7035555555</contact:voice> C: <contact:fax>+1.7035555556</contact:fax> C: <contact:email>[email protected]</contact:email> C: <contact:authInfo> C: <contact:pw>2fooBAR</contact:pw> C: </contact:authInfo> C: <contact:disclose flag="0"> C: <contact:voice/> C: <contact:email/> C: </contact:disclose> C: </contact:create> C: </create> C: <extension> C: <addlEmail:addlEmail C: xmlns:addlEmail="urn:ietf:params:xml:ns:epp:addlEmail-1.0"> C: <addlEmail:email primary="true">麥克風@example.com</addlEmail:email> C: </addlEmail:addlEmail> C: </extension> C: <clTRID>ABC-12345</clTRID> C: </command> C:</epp>
This extension does not add any elements to the EPP <create> response described in [RFC5730].¶
This extension does not add any elements to the EPP <delete> command or <delete> response described in [RFC5730].¶
This extension does not add any elements to the EPP <renew> command or <renew> response described in [RFC5730].¶
This extension does not add any elements to the EPP <transfer> command or <transfer> response described in [RFC5730].¶
This extension defines additional elements to extend the EPP <update> command of an object mapping like [RFC5733].¶
The EPP <update> command provides a transform operation that allows a client to update an instance of an object. In addition to the EPP command elements described in an object mapping like [RFC5733], the command MUST contain a child <addlEmail:addlEmail> element (Section 4) for the client to be set or unset an alternate email. If the alternate email does not apply to the object, the server MUST return an EPP error result code of 2201.¶
The following is an example <update> command to set a contact object with an alternate ASCII email:¶
C:<?xml version="1.0" encoding="UTF-8" standalone="no"?> C:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0"> C: <command> C: <update> C: <contact:update C: xmlns:contact="urn:ietf:params:xml:ns:contact-1.0"> C: <contact:id>sh8013</contact:id> C: </contact:update> C: </update> C: <extension> C: <addlEmail:addlEmail C: xmlns:addlEmail="urn:ietf:params:xml:ns:epp:addlEmail-1.0"> C: <addlEmail:email>[email protected]</addlEmail:email> C: </addlEmail:addlEmail> C: </extension> C: <clTRID>ABC-12345</clTRID> C: </command> C:</epp>
The following is an example <update> command to set a contact object with an alternate SMTPUTF8 email address:¶
C:<?xml version="1.0" encoding="UTF-8" standalone="no"?> C:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0"> C: <command> C: <update> C: <contact:update C: xmlns:contact="urn:ietf:params:xml:ns:contact-1.0"> C: <contact:id>sh8013</contact:id> C: </contact:update> C: </update> C: <extension> C: <addlEmail:addlEmail C: xmlns:addlEmail="urn:ietf:params:xml:ns:epp:addlEmail-1.0"> C: <addlEmail:email>麥克風@example.com</addlEmail:email> C: </addlEmail:addlEmail> C: </extension> C: <clTRID>ABC-12345</clTRID> C: </command> C:</epp>
The following is an example <update> command to unset a contact object alternate email address:¶
C:<?xml version="1.0" encoding="UTF-8" standalone="no"?> C:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0"> C: <command> C: <update> C: <contact:update C: xmlns:contact="urn:ietf:params:xml:ns:contact-1.0"> C: <contact:id>sh8013</contact:id> C: </contact:update> C: </update> C: <extension> C: <addlEmail:addlEmail C: xmlns:addlEmail="urn:ietf:params:xml:ns:epp:addlEmail-1.0"> C: <addlEmail:email/> C: </addlEmail:addlEmail> C: </extension> C: <clTRID>ABC-12345</clTRID> C: </command> C:</epp>
This extension does not add any elements to the EPP <create> response described in [RFC5730].¶
The EPP Additional Email Address Extension schema is presented here.¶
The formal syntax shown here is a complete XML Schema representation of the object mapping suitable for automated validation of EPP XML instances. The <CODE BEGINS> and <CODE ENDS> tags are not part of the XML Schema; they are used to note the beginning and ending of the XML Schema for URI registration purposes.¶
<CODE BEGINS>
<?xml version="1.0" encoding="UTF-8"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
xmlns:addlEmail="urn:ietf:params:xml:ns:epp:addlEmail-1.0"
targetNamespace="urn:ietf:params:xml:ns:epp:addlEmail-1.0"
elementFormDefault="qualified">
<annotation>
<documentation>Extensible Provisioning Protocol v1.0
additional email address schema.</documentation>
</annotation>
<!-- Create, Update, and Info Response extension element -->
<element name="addlEmail" type="addlEmail:addlEmailType" />
<!--
Single email element that can be empty
-->
<complexType name="addlEmailType">
<sequence>
<element name="email" type="addlEmail:emailType"/>
</sequence>
</complexType>
<complexType name="emailType">
<simpleContent>
<extension base="token">
<attribute name="primary" type="boolean" default="false"/>
</extension>
</simpleContent>
</complexType>
<!--
End of schema.
-->
</schema>
<CODE ENDS>¶
This document uses URNs to describe XML namespaces conforming to a registry mechanism described in RFC 3688 [RFC3688]. The following URI assignment should be made by IANA:¶
Registration request for the addlEmail namespace:¶
Registration request for the addlEmail XML Schema:¶
The EPP extension described in this document should be registered by IANA in the "Extensions for the Extensible Provisioning Protocol (EPP)" registry described in RFC 7451 [RFC7451]. The details of the registration are as follows:¶
Note to RFC Editor: Please remove this section and the reference to RFC 7942 [RFC7942] before publication.¶
This section records the status of known implementations of the protocol defined by this specification at the time of posting of this Internet-Draft, and is based on a proposal described in RFC 7942 [RFC7942]. The description of implementations in this section is intended to assist the IETF in its decision processes in progressing drafts to RFCs. Please note that the listing of any individual implementation here does not imply endorsement by the IETF. Furthermore, no effort has been spent to verify the information presented here that was supplied by IETF contributors. This is not intended as, and must not be construed to be, a catalog of available implementations or their features. Readers are advised to note that other implementations may exist.¶
According to RFC 7942 [RFC7942], "this will allow reviewers and working groups to assign due consideration to documents that have the benefit of running code, which may serve as evidence of valuable experimentation and feedback that have made the implemented protocols more mature. It is up to the individual working groups to use this information as they see fit".¶
Organization: Verisign Inc.¶
Name: Verisign EPP SDK¶
Description: The Verisign EPP SDK includes both a full client implementation and a full server stub implementation of draft-ietf-regext-epp-eai.¶
Level of maturity: Development¶
Coverage: All aspects of the protocol are implemented.¶
Licensing: GNU Lesser General Public License¶
Contact: [email protected]¶
URL: https://www.verisign.com/en_US/channel-resources/domain-registry-products/epp-sdks¶
As is noted in Section 10.1 and Section 13 of [RFC6530], unconstrained Unicode in email addresses can introduce a class of security threats that do not exist with all-ASCII email addresses. As EPP exists in ecosystems where email addresses passed in EPP are displayed in RDAP and other services, and copy-and-paste of these email addresses is common for businesses transferring domains via EPP, there should be safeguards against these threats. Therefore, use of the SMTPUTF8 email addresses as described in this document SHOULD be done with policies that disallow the use of unconstrained Unicode. The domain-part of these SMTPUTF8 email addresses SHOULD conform to IDNA2008. The local-part of these SMTPUTF8 email addresses SHOULD be restricted to Unicode that does not introduce the threats noted in [RFC6530]. One such possible solution would be to disallow characters outside of Unicode Annex 31 (https://unicode.org/reports/tr31/).¶
As email address is often a primary end user contact, and an invalid email address may put communication with the end user at risk when such contact is necessary. In case of an invalid domain name in the email address a malicious actor can register a valid domain name with similar U-label (homograph attack) and assume control over the domain name associated with the contact using social engineering techniques. To reduce the risk of the use of invalid domain names in email addresses, registries SHOULD validate the domain name syntax in provided email addresses and validate whether the domain name consists of the code points allowed by IDNA Rules and Derived Property Values.¶
Note that the syntax for internationalized email localparts is very liberal. Domains are normalized during MX lookup, while localparts are unconstrained. Implementers may wish to test that their database is able to store difficult localparts such as U+0061 U+0300 U+00E0. For more on normalization and these three code points, see [RFC5198] Section 3.¶
In cases where a contact object contains two email addresses, be aware that either address may be forwarded to the other. This implies that a message sent to an all-ASCII address may receive a reply from an SMTPUTF8 address, or vice versa.¶
The authors would like to thank Alexander Mayrhofer, Chris Lonvick, Gustavo Lozano, Jody Kolker, John C Klensin, John Levine, Klaus Malorny, Marc Blanchet, Marco Schrieck, Mario Loffredo, Murray S. Kucherawy, Patrick Mevzek, Pete Resnick, Takahiro Nemoto, Taras Heichenko, Arnt Gulbrandsen, and Thomas Corte for their careful review and valuable comments.¶