This Enumservice indicates that the resource can be identified by the associated 'acct' URI [RFC7565].

This Enumservice indicates that the resource can be addressed by the associated URI in order to send an email.

This Enumservice indicates that the resource identified by the associated URI is capable of receiving a message using an email protocol.

EMS content is sent over SMTP using the format specified by TS 23.140 [15] Section 8.4.4 and TS 26.140 [16] Section 4, as an MMS message. Within such a message, EMS content is carried as either a text or application/octet-stream MIME sub-part (see TS 26.140 [16], Section 4.1).

For references see [RFC4355].

There are no specific security issues with this Enumservice. However, the general considerations of Section 6 of [RFC4355] apply.

This Enumservice indicates that the resource identified by the associated URI is capable of receiving a message using the Enhanced Message Service (EMS) [14] (For reference see [RFC4355]).

There are no specific security issues with this Enumservice. However, the general considerations of Section 6 of [RFC4355] apply.

Note that an indication of EMS can be taken as implying that the recipient is capable of receiving SMS messages at this address as well.

This Enumservice indicates that the resource identified by the associated URI is capable of being contacted to provide a communication session during which facsimile documents can be sent.

A client selecting this NAPTR will have support for generating and sending facsimile documents to the recipient using the PSTN session and transfer protocols specified in [12] and [13] in [RFC4355] - in short, they will have a fax program with a local or shared PSTN access over which they can send faxes.

References are contained in [RFC4355].

This Enumservice indicates that the resource identified by the associated URI is a file service from which a file or file listing can be retrieved.

The 'iax' Enumservice is used to map E.164 numbers to IAX URIs. Such URIs identify resources capable of being contacted to provide a communication session using the IAX protocol [RFC5456].

A client selecting this NAPTR needs to be able to support communication utilizing the IAX protocol.

This Enumservice indicates that the resource identified can be addressed by the associated URI in order to access a user's calendar (for example free/busy status) using the CalDAV [7] protocol for Internet calendaring.

References are contained in [RFC5333].

This Enumservice indicates that the resource identified can be addressed by the associated URI in order to access a user's calendar (for example free/busy status) using the CalDAV [7] protocol for Internet calendaring.

References are contained in [RFC5333].

This Enumservice indicates that the resource identified can be addressed by the associated URI used for scheduling using Internet calendaring via Internet mail with the iMIP [6] protocol.

References are contained in [RFC5333].

The URI Scheme is 'mailto' because facsimile is a profile of standard Internet mail and uses standard Internet mail addressing.

This Enumservice indicates that the resource identified is an 'im:' URI. The 'im:' URI scheme does not identify any particular protocol that will be used to handle instant messaging receipt or delivery, rather the mechanism in RFC3861 [4] is used to discover whether an IM protocol supported by the party querying ENUM is also supported by the target resource.

References are contained in [RFC5028].

This Enumservice indicates that the resource identified by the associated URI is capable of receiving a message using an email protocol.

MMS messages are sent over SMTP using the format specified by TS 23.140 [15] Section 8.4.4 and TS 26.140 [16] Section 4.

Within and between MMS Environments (MMSE, network infrastructures that support the MultiMedia Service), other pieces of state data (for example, charging-significant information) are exchanged between MMS Relay Servers. Thus, although these servers use SMTP as the "bearer" for their application exchanges, they map their internal state to specialized header fields carried in the SMTP message exchanges. The header fields used in such MMSE are described in detail in [17].

For references see [RFC4355].

There are no specific security issues with this Enumservice. However, the general considerations of Section 6 of [RFC4355] apply.

The MMS Architecture describes an interface between the MMSE and "legacy messaging systems" (labelled as MM3) which accepts "standard" SMTP messages. Thus although the MMS Relay Server that supports this interface appears as a standard SMTP server from the perspective of an Internet-based mail server, it acts as a gateway and translator, adding the internal state data that is used within and between the MMS Environments. This mechanism is described in [17], which also includes references to the specifications agreed by those bodies responsible for the design of the MMS.

References are contained in [RFC4355].

This Enumservice indicates that the resource identified by the associated URI is capable of receiving a message using the Multimedia Messaging Service (MMS) [15].

For references see [RFC4355].

There are no specific security issues with this Enumservice. However, the general considerations of Section 6 of [RFC4355] apply.

Note that MMS can be used as an alternative to deliver an SMS RP-DATA RPDU if, for example, the SMS bearer is not supported. If an entry includes this Enumservice, then in effect this can be taken as implying that the recipient is capable of receiving EMS or SMS messages at this address. Such choices on the end system de do have two small caveats; whilst in practice all terminals supporting MMS today support SMS as well, it might not necessarily be the case in the future, and there may be tariff differences in using the MMS rather than using the SMS or EMS.

See [RFC3953], Section 3.

These Enumservices indicate that the resource identified can be addressed by the associated URI in order to initiate a telecommunication session, which may include two-way voice or other communications, to the PSTN.

A Number Portability Dip Indicator (npdi) should be used in practice (see [RFC4769], Section 4).

These Enumservices indicate that the resource identified can be addressed by the associated URI in order to initiate a telecommunication session, which may include two-way voice or other communications, to the PSTN. These URIs may contain number portability data as specified in RFC4694 [10].

References are contained in [RFC4769].

A Number Portability Dip Indicator (npdi) should be used in practice (see [RFC4769], Section 4).

See [RFC3764], Section 3.

This Enumservice indicates that the resource identified by the associated URI is capable of receiving a message using an email protocol.

SMS content is sent over SMTP using the format specified by TS 23.140 [15] Section 8.4.4 and TS 26.140 [16] Section 4, as an MMS message. Within such a message, SMS content is carried as either a text or application/octet-stream MIME sub-part (see TS 26.140 [16], Section 4.1)

For references see [RFC4355]

There are no specific security issues with this Enumservice. However, the general considerations of Section 6 of [RFC4355] apply.

This Enumservice indicates that the resource identified by the associated URI is capable of receiving a message using the Short Message Service (SMS) [14] in [RFC4355].

There are no specific security issues with this Enumservice. However, the general considerations of Section 6 of [RFC4355] apply.

This Enumservice indicates that the resource identified by the associated URI scheme is capable of being a source of information.

Note that the kind of information retrieved can be manifold. Usually, contacting a resource by an 'http:' [11] URI provides a document. This document can contain references that will trigger the download of many different kinds of information, such as text, audio, video, executable code, or even video message files. Thus, one cannot be more specific about the kind of information expected when contacting the resource.

References are contained in [RFC5278].

Implementers should review a non-exclusive list of examples in Section 7 of [RFC5278].

This Enumservice indicates that the resource identified by the associated URI scheme is capable of being a source of information, which can be contacted using TLS or the Secure Socket Layer protocol.

Note that the kind of information retrieved can be manifold. Usually, contacting a resource by an 'https:' [12] URI provides a document. This document can contain references that will trigger the download of many different kinds of information, such as text, audio, video, executable code, or even video message files. Thus, one cannot be more specific about the kind of information expected when contacting the resource.

References are contained in [RFC5278].

Implementers should review a non-exclusive list of examples in Section 7 of [RFC5278].

This Enumservice indicates that the resource identified can be addressed by the associated URI scheme in order to initiate a unified communication session to a unified messaging system.

Implementers should review a non-exclusive list of examples in Section 7 of [RFC5278].

This Enumservice indicates that the resource identified can be addressed by the associated URI scheme in order to initiate a unified communication session to a unified messaging system.

Implementers should review a non-exclusive list of examples in Section 7 of [RFC5278].

This Enumservice indicates that the resource identified is a plain vCard, according to RFC2426, which may be accessed using HTTP / HTTPS [7].

Clients fetching the vCard from the resource indicated should expect access to be restricted. Additionally, the comprehension of the data provided may vary depending on the client's identity.

References are contained in [RFC4969].

This Enumservice indicates that the resource identified by the associated URI scheme is capable of being a source of information.

Note that the kind of information retrieved can be manifold. Usually, contacting a resource by an 'http:' [11] URI provides a document. This document can contain references that will trigger the download of many different kinds of information, such as text, audio, video, executable code, or even video message files. Thus, one cannot be more specific about the kind of information expected when contacting the resource.

References are contained in [RFC5278].

Implementers should review a non-exclusive list of examples in Section 7 of [RFC5278].

This Enumservice indicates that the resource identified by the associated URI scheme is capable of being a source of information, which can be contacted using TLS or the Secure Socket Layer protocol.

Note that the kind of information retrieved can be manifold. Usually, contacting a resource by an 'https:' [12] URI provides a document. This document can contain references that will trigger the download of many different kinds of information, such as text, audio, video, executable code, or even video message files. Thus, one cannot be more specific about the kind of information expected when contacting the resource.

References are contained in [RFC5278].

Implementers should review a non-exclusive list of examples in Section 7 of [RFC5278].

This Enumservice indicates that the resource identified can be addressed by the associated URI scheme in order to initiate a video communication session to a video messaging system.

Implementers should review a non-exclusive list of examples in Section 7 of [RFC5278].

This Enumservice indicates that the resource identified can be addressed by the associated URI scheme in order to initiate a video communication session to a video messaging system.

Implementers should review a non-exclusive list of examples in Section 7 of [RFC5278].

The kind of communication indicated by this Enumservice is "Interactive Voice". From a protocol perspective, this communication is expected to involve bidirectional media streams carrying audio data.

A client may imply that the person controlling population of a NAPTR holding this Enumservice indicates their capability to engage in an interactive voice session when contacted using the URI generated by this NAPTR.

This Enumservice indicates that the person responsible for the NAPTR is accessible via the PSTN (Public Switched Telephone Network) or PLMN (Public Land Mobile Network) using the value of the generated URI.

The kind of subsystem required to initiate a Voice Enumservice with this Subtype is a "Dialler". This is a subsystem that either provides a local connection to the PSTN or PLMN, or that provides an indirect connection to those networks. The subsystem will use the telephone number held in the generated URI to place a voice call. The voice call is placed to a network that uses E.164 numbers to route calls to an appropriate destination.

Note that the PSTN/PLMN connection may be indirect. The end user receiving this NAPTR may have a relationship with a Communications Service Provider that accepts call initiation requests from that subsystem using an IP-based protocol such as SIP or H.323, and places the call to the PSTN using a remote gateway service. In this case the Provider may either accept requests using "tel:" URIs or has a defined mechanism to convert "tel:" URI values into a "protocol-native" form.

The "tel:" URI value SHOULD be fully qualified (using the "global phone number" form of RFC3966 [10]). A "local phone number" as defined in that document SHOULD NOT be used unless the controller of the zone in which the NAPTR appears is sure that it can be distinguished unambiguously by all clients that can access the resource record and that a call from their network access points can be routed to that destination.

References are contained in [RFC4415].

This Enumservice indicates that the resource identified by the associated URI scheme is capable of being a source of information.

Note that the kind of information retrieved can be manifold. Usually, contacting a resource by an 'http:' [11] URI provides a document. This document can contain references that will trigger the download of many different kinds of information, such as text, audio, video, executable code, or even voice message files. Thus, one cannot be more specific about the kind of information expected when contacting the resource.

References are contained in [RFC5278].

Implementers should review a non-exclusive list of examples in Section 7 of [RFC5278].

This Enumservice indicates that the resource identified by the associated URI scheme is capable of being a source of information, which can be contacted using TLS or the Secure Socket Layer protocol.

Note that the kind of information retrieved can be manifold. Usually, contacting a resource by an 'https:' [12] URI provides a document. This document can contain references that will trigger the download of many different kinds of information, such as text, audio, video, executable code, or even voice message files. Thus, one cannot be more specific about the kind of information expected when contacting the resource.

References are contained in [RFC5278].

Implementers should review a non-exclusive list of examples in Section 7 of [RFC5278].

This Enumservice indicates that the resource identified can be addressed by the associated URI scheme in order to initiate a voice communication session to a voice messaging system.

Implementers should review a non-exclusive list of examples in Section 7 of [RFC5278].

This Enumservice indicates that the resource identified can be addressed by the associated URI scheme in order to initiate a voice communication session to a voice messaging system.

Implementers should review a non-exclusive list of examples in Section 7 of [RFC5278].

This Enumservice indicates that the resource identified can be addressed by the associated URI scheme in order to initiate a voice communication session to a voice messaging system.

Implementers should review a non-exclusive list of examples in Section 7 of [RFC5278].

Malicious Redirection: One of the fundamental dangers related to any service such as this is that a malicious entry in a resolver's database will cause clients to resolve the E.164 into the wrong LDAP URI. The possible intent may be to cause the client to connect to a rogue LDAP server and retrieve (or fail to retrieve) a resource containing fraudulent or damaging information.

Denial of Service: By removing the URI to which the E.164 maps, a malicious intruder may remove the client's ability to access the LDAP directory server.

Malicious Redirection: One of the fundamental dangers related to any service such as this is that a malicious entry in a resolver's database will cause clients to resolve the E.164 into the wrong email URI. The possible intent may be to cause the client to send the information to an incorrect destination.

Denial of Service: By removing the URI to which the E.164 maps, a malicious intruder may remove the client's ability to access the resource.

Unsolicited Bulk Email: The exposure of email addresses through the ENUM service provides a bulk mailer access to large numbers of email addresses where only the telephone number was previously known.

Error Conditions:

E.164 number not in the numbering plan

E.164 number in the numbering plan, but no URIs exist for that number

E2U+vpim:mailto Service unavailable of email addresses where only the telephone number was previously known.

This Enumservice indicates that the resource identified by the associated URI is capable of being a source of information. It has to be noted that the kind of information retrieved can be manifold. Usually, contacting a resource by an "http:" URI provides a document. This document can contain references that will trigger download of many different kinds of information, like audio or video or executable code. Thus, one can not be more specific about the kind of information that can be expected when contacting the resource.

This Enumservice indicates that the resource identified by the associated URI is capable of being a source of information, which can be contacted by using TLS or Secure Socket Layer protocol. It has to be noted that the kind of information retrieved can be manifold. Usually, contacting a resource by an "https:" URI provides a document. This document can contain all different kind of information, like audio or video or executable code. Thus, one can not be more specific what information to expect when contacting the resource.

This Enumservice indicates that the resource identified is an XMPP entity.