A.129	user agent (UA)
F: agent d'usager (AU)
S: agente de usuario (AU)
	In the context of message handling, the functional object, a component of MHS, by means of which a single direct user engages in message handling.
	Component of MHS the user interacts with.
ANNEX B
(to Recommendation X.400)
Definitions of elements of service
	Note – The abbreviations used in the title lines have the following meanings:
	TM		Message transfer
	IPM		Interpersonal messaging
	PD		Physical delivery
	MS		Message store
	PR		Per recipient (available on a per–recipient basis)
B.1	Access management	TM
	This element of service enables a UA and MTA to establish access to one another and to manage information associated with access establishment.
	The element of service permits the UA and MTA to identify and validate the identity of the other. It provides a capability for the UA to specify its O/R address and to maintain access security. When access security is achieved through passwords, these passwords can be periodically updated.
	Note – A more secure form of access management is provided by the element of service secure access management.
B.2	Additional physical rendition	PD	PR
	This element of service allows an originating user to request the PDAU to provide the additional renditon facilities (e.g., kind of paper, colour printing, etc.). Bilateral agreement is required to use this element of service.
B.3	Alternate recipient allowed	MT
	This element of service enables an originating UA to specify that the message being submmitted can be delivered to an alternate recipient as described below.
	A destination MD will interpret all of the user attributes in order to select a recipient UA. Three cases can be distinguished:
1)	all the attributes match precisely those of a subscriber UA. Delivery is attempted to that UA;
2)	either insufficient attributes are supplied or those supplied match those of more than one subscriber UA. The message cannot be delivered;
3)	at least the minimum set of attributes required by the destination MD is supplied. Nevertheless, taking all of the other attributes into account, the attributes match those of no UA.
	In case 3, an MD that supports the alternate recipient assignment element of service can deliver the message to a UA that has been assinged to receive such messages. This UA will be notified of the O/R address of the intended recipient as specified by the originator. Delivery to this UA will be reported in a delivery notification if requested by the originator.
B.4	Alternate recipient assignment	MT
	This element of service enables a UA to be given the capability to have certain messages delivered to it for which there is not an exact match between the recipient attributes specified and the name of the user. Such a UA is specified in terms of one or more attributes for which an exact match is required, and one or more attributes for which any value is acceptable. For example, an orginization can establish a UA to receive all messages for which country name, administration management domain name and organization name (for example, company name) are an exact match but the personal name of the recipient does not correspond to an individual known by an MHS in that organization. This permits the organization to manually handle the messages to these individuals.
	In order for a message to be reassigned to an alternate recipient, the originator must have requested the alternate recipient allowed element of service.
B.5	Authorizing users indication	IPM
	This element of service allows the originator to indicate to the recipient the names of the one or more persons who authorized the sending of the message. For example, an individual can authorize a particular action which is subsequently communicated to those concerned by another person such as a secretary. The former person is said to authorize its sending while the latter person is the one who sent the message (originator). This does not imply signature‑level authorization.
B.6	Auto–forwarded indication	IPM
	This element of service allows a recipient to determine that a body of an incoming IP–message contains an IP–message that has been auto–forwarded. Thus the recipient can distinguish from that where an incoming IP‑message contains a forwarded message (as described in § B–31) in the body. As with a forwarded IP–message, an auto–forwarded IP–message can be accompanied by information (for example, time stamps, indication of conversion) associated with its original delivery.
	Note – The indication that auto–forwarding of an IP–message has occurred enables a recipient IPM UA, should it so choose, to prevent further auto–forwarding and thus the possibility of loops. In addition, a recipient IPM UA can choose whether or not to auto–forward based on other criteria (for example, sensitivity classification).
	When an IPM UA auto–forwards an IP–message, it designates it as auto–forwarded. If receipt/non–receipt notification has been requested for the IP–message being auto–forwarded, the IPM UA generates a non–receipt notification informing the originator of the auto–forwarding of the IP–message. The notification optionally includes a comment supplied by the originally intended recipient. No further notification applying to the auto–forwarded IP‑message is generated by any IPM UA.
B.7	Basic physical rendition	PD	PR
	This element of service enables the PDAU to provide the basic renditon facilities for converting the MHS message into a physical message. This is the default action to be taken by the PDAU.
B.8	Blind copy recipient indication	IPM	PR
	This element of service allows the originator to provide the O/R name of one or more additional users, or DLs, who are intended recipients of the IP–message being sent. These names are not disclosed to either the primary or copy recipients. Whether or not these additional recipients are disclosed to one another is a local matter.
B.9	Body part encryption indication	IPM
	This element of service allows the originator to indicate to the recipient that a particular body of the IP‑message being sent has been encrypted. Encryption can be used to prevent unauthorized inspection or modification of the body part. This element of service can be used by the recipient to determine that some body part(s) of the IP‑message must be decrypted. This element of service, however, does not itself encrypt or decrypt any body part.
B.10	Content confidentiality	MT
	This element of service allows the originator of a message to protect the content of the message from disclosure to recipients other than the intended recipient(s). Content confidentiality is on a per–message basis, and can use either an asymmetric or a symmetric encryption technique.
B.11	Content integrity	MT	PR
	This element of service allows the originator of the message to provide to the recipient of the message a means by which the recipient can verify that the content of the message has not been modified. Content integrity is on a per–recipient basis, and can use either an asymmetric or a symmetric encryption technique.
B.12	Content type indication	MT
	This element of service enables an originating UA to indicate the content type for each submitted message. A recipient UA can have one or more content types delivered to it. An example of a content type is the contents generated by the IPM class of cooperating UAs.
B.13	Conversion prohibition	MT
	This element of service enables an originating UA to instruct the MTS that implicit encoded information type conversion(s) should not be performed for a particular submitted message.
B.14	Conversion prohibition in case of loss of information	MT
	This element of service enables an originating UA to instruct the MTS that encoded information type conversion(s) should not be performed for a particular submitted message if such conversion(s) would result in loss of information. Loss of information is discussed in detail in X.408.
	Should this and the conversion prohibition element of service both be selected, the latter shall take precedence.
	Note – This element of service will not protect against possible loss of information in certain cases where the recipient is using an I/O device whose capabilities are unknown to the MTA.
B.15	Converted indication	MT	PR
	This element of service enables the MTS to indicate to a recipient UA that the MTS performed encoded information type conversion on a delivered message. The recipient UA is informed of the resulting types.
B.16	Counter collection	PD	PR
	This element of service allows an originating user to instruct the PDS to keep the physical message ready for counter collection at the post office specified by the originator, or at the post office which offers counter collection service closest to the given recipient's address.
B.17	Counter collection with advice	PD	PR
	This element of service allows an originating user to instruct the PDS to keep the physical message ready for counter collection at the post office specified by the originator, or at the post office which offers counter collection service closest to the given recipient's address, and to inform the recipient via telephone, or telex, or teletex, using the number provided by the originator.
B.18	Cross–referencing indication	IPM
	This element of service allows the originator to associate with the IP–message being sent, the globally unique identifiers of one or more other IP–messages. This enables the recipient's IPM UA, for example, to retrieve from storage a copy of the referenced IP–messages.
B.19	Deferred delivery	MT
	This element of service enables an originating UA to instruct the MTS that a message being submitted shall be delivered no sooner than a specified data and time. Delivery will take place as close to the date and time specified as possible, but not before. The date and time specified for deferred delivery is subject to a limit which is defined by the originator's management domain.
	Note – Storage of the message shall be handled in the originating country.
B.20	Deferred delivery cancellation	MT
	This element of service enables an originating UA to instruct the MTS to cancel a previously submitted deferred delivery message. The cancellation attempt may or may not always succeed. Possible reasons for failure are: deferred delivery time has passed, or the message has already been forwarded within the MTS.
B.21	Delivery notification	MT	PR
	This element of service enables an originating UA to request that the originating UA be explicitly notified when a submitted message has been successfully delivered to a recipient UA or access unit. The notification is related to the submitted message by means of the message indentifier and includes the date and time of delivery. In the case of a multi–destination message, the originating UA can request this element of service or a per–recipient basis.
	When a message is delivered after distribution list expansion, then, depending on the policy of the distribution list, the notification can be sent to either the list owner, the message originator, or both.
	Delivery notification carries no implication that any UA or user action, such as examination of the message content, has taken place.
B.22	Delivery time stamp indication	MT	PR
	This element of service enables the MTS to indicate to a recipient UA the date and time at which the MTS delivered a message. In the case of physical delivery, this element of service indicates the date and time at which the PDAU has taken responsibility for printing and further delivery of the physical message.
B.23	Delivery via bureaufax service	PD	PR
	This element of service allows an originating user to instruct the PDAU and associated PDS to use the bureaufax service for transport and delivery.
B.24	Designation of recipient by directory name	MT	PR
	This element of service enables an originating UA to use a directory name in place of an individual recipient's O/R address.
B.25	Disclosure of other recipients	MT
	This element of service enables the originating UA to instruct the MTS then submitting a multi–recipient message, to disclose the O/R names of all other recipients to each recipient UA, upon delivery of the message. The O/R names disclosed are as supplied by the originating UA. If distribution list expansion has been performed, then only the originator specified DL name will be disclosed, and not the names of its members.
B.26	DL expansion history indication	MT
	This element of service provides to a recipient, at delivery, information about the distribution list(s) through which the message has arrived. It is a local matter as to how much of this information is presented to the recipient.
B.27	DL expansion prohibited	MT
	This element of service allows an originating user to specify that if any of the recipients can directly or via reassignment refer to a distribution list, then no expansion shall occur. Instead, a non–delivery notification will be returned to the originating UA, unless prevention of non–delivery notification has been requested.
B.28	EMS (express mail service)	PD	PR
	This element of service allows an originating user to instruct the PDS to transport and deliver the physical message produced from the MHS message through accelerated letter circulation and delivery service (such as EMS or the equivalent domestic service) in the destination country.
B.29	Expiry date indication	IPM
	This element of service allows the originator to indicate to the recipient the date and time after which he considers the IP–message to be invalid. The intent of this element of service is to state the originator's assessment of the current applicability of an IP–message. The particular action on behalf of a recipient by his IPM UA, or by the recipient himself, is unspecified. Possible actions might be to file or delete the IP–message after the expiry date has passed.
B.30	Explicit conversion	MT	PR
	This element of service enables an originating UA to request the MTS to perform a specified conversion, such as required when interworking between different telematic services. When a message is delivered after conversion has been performed, the recipient UA is informed of the original encoded information types as well as the current encoded information types in the message.
	Note 1 – This element of service is intended to support interworking with telematic terminals/services.
	Note 2 – When DL names are used in conjunction with this element of service, conversion will apply to all members of the DL.
B.31	Forwarded IP–message indication	IPM
	This element of service allows a forwarded IP–message, or a forwarded IP–message plus its “delivery information” to be sent as the body (or as one of the body parts) of an IP–message. An indication that the body part is forwarded is conveyed along with the body part. In a multi–part body, forwarded body parts can be included along with body parts of other types. “Delivery information” is information which is conveyed from the MTS when an IP‑message is delivered (for example, time stamps and indication of conversion). However, inclusion of this delivery information along with a forwarded IP–message in no way guarantees that this delivery information is validated by the MTS.
	The receipt notification request indication and the non–receipt notification request elements of service are not affected by the forwarding of a IP–message.
B.32	Grade of delivery selection	MT
	This element of service enables an originating UA to request that transfer through the MTS be urgent or non‑urgent, rather than normal. The time periods defined for non–urgent and urgent transfer are longer and shorter, respectively, than that defined for normal transfer. This indication is also sent to the recipient with the message.
B.33	Hold for delivery	MT
	This element of service enables a recipient UA to request that the MTS hold its messages and returning notifications for delivery until a later time. The UA can indicate to the MTS when it is unavailable to take delivery of messages and notifications, and also, when it is again ready to accept delivery of messages and notifications from the MTS. The MTS can indicate to the UA that messages are waiting due to the criteria the UA established for holding messages. Responsibility for the management of this element of service lies with the recipient MTA.
	Criteria for requesting a message to be held for delivery are: encoded information type, content type, maximum content length, and priority. The message will be held until the maximum delivery time for that message expires, unless the recipient releases the hold prior to its expiry.
	Note – The hold for delivery element of service is distinct from the message store facility. The hold for delivery element of service provides temporary storage to facilitate delivery and only after a message has been transferred to the recipient's UA, is delivery notification returned. The message store facility augments the storage of a UA and can be used to store messages for an extended period of time. Unlike the hold for delivery element of service, delivery notifications are returned as soon as the message is placed in (that is, delivered to) the message store.
B.34	Implicit conversion	MT
	This element of service enables a recipient UA to have the MTS perform for a period of time any necessary conversion on messages prior to delivery. Neither the originating nor recipient UA explicitly requests this element of service on a per–message basis. If the encoded information type capabilities of the recipient UA are such that more than one type of conversion can be performed, the most appropriate conversion is performed. When a message is delivered after conversion has been performed, the recipient UA is informed of the original encoded information types as well as the current encoded information types in the message.
B.35	Importance indication	IPM
	This element of service allows the originator to indicate to the recipients his assessment of the importance of the IP–message being sent. Three levels of importance are defined: low, normal, and high.
	This element of service is not related to the grade of delivery selection element of service provided by the MTS. The particular action taken by the recipient or his IPM UA based on the importance categorization is unspecified. It is the intent to allow the recipient IPM UA, for example, to present IP–messages in order of their importance or to alert the recipient of the arrival of IP–messages of high importance.
B.36	Incomplete copy indication	IPM
	This element of service allows an originator to indicate that this IP–message is an incomplete copy of an IP‑message with the same IP–message identification in that one or more body parts, and/or heading fields of the original IP–message are absent.
B.37	IP–message identification	IPM
	This element of service enables cooperating IMP UAs to convey a globally unique identifier for each IP‑message sent or received. The IP–message identifier is composed of an O/R name of the originator and an identifier that is unique with respect to that name. IPM UAs and users use this identifier to refer to a previously sent or received IP–message (for example, in receipt notifications).
B.38	Language indication	IPM
	This element of service enables an originating UA to indicate the language type(s) of a submitted IP‑message.
B.39	Latest delivery designation	MT
	This element of service enables an originating UA to specify the latest time by which the message is to be delivered. If the MTS cannot deliver by the time specified, the message is not delivered and is cancelled. On multi‑recipient messages, the latest delivery time can expire prior to delivery to all recipients, but this will not negate any deliveries which have already occurred.
B.40	Message flow confidentiality	MT
	This element of service allows the originator of the message to protect information which might be derived from observation of the message flow.
	Note – Only a limited form of this is supported.
B.41	Message identification	MT
	This element of service enables the MTS to provide a UA with a unique identifier for each message or probe submitted or delivered by the MTS. UAs and the MTS use this identifier to refer to a previously submitted message in connection with elements of service such as delivery and non–delivery notification.
B.42	Message origin authentication	MT	PR
	This element of service allows the originator of a message to provide to the recipient(s) of the message, and any MTA through which the message is transferred, a means by which the origin of the message can be authenticated (i.e. a signature). Message origin authentication can be provided to the recipient(s) of the message, and any MTA through which the message is transferred, on a per–message basis using an asymmetric encryption technique, or can be provided only to the recipient(s) of the message, on a per–recipient basis using either an asymmetric or a symmetric encryption technique.
B.43	Message security labelling	MT
	This element of service allows the originator of a message (or probe) to associate with the message (and any reports on the message or probe) an indication of the sensitivity of the message (a security label). The message security label may be used by the MTS and the recipient(s) of the message to determine the handling of the message in line with the security policy in force.
B.44	Message sequence integrity	MT	PR
	This element of service allows the originator of the message to provide to a recipient of the message a means by which the recipient can verify that the sequence of messages from the originator to the recipient has been preserved (without message loss, re–ordering, or replay). Message sequence integrity is on a per–recipient basis, and can use either an asymmetric or a symmetric encryption technique.
B.45	Multi–destination delivery	MT	PR
	This element of service enables an originating UA to specify that a message being submitted is to be delivered to more than one recipient UA. Simultaneous delivery to all specified UAs is not implied by this element of service.
B.46	Multi–part body	IPM
	This element of service allows an originator to send to a recipient or recipients an IP–message with a body that is partitioned into several parts. The nature and attributes, or type, of each body part are conveyed along with the body part.
B.47	Non–delivery notification	MT	PR
	This element of service enables the MTS to notify an originating UA if a submitted message was not delivered to the specified recipient UA(s). The reason the message was not deliverd is included as part of the notification. For example, the recipient UA can be unknown to the MTS.
	In the case of a multi–destination message, a non–delivery notification can refer to any or all of the recipient UAs to which the message could not be delivered.
	When a message is not delivered after distribution list expansion, then, depending on the policy of the distribution list, the notification can be sent to either the list owner, the message originator, or both.
B.48	Non–receipt notification request indication	IPM	PR
	This element of service allows the originator to ask that he be notified should the IP–message be deemed unreceivable. In the case of a multi–recipient IP–message, the originator can request this element of service on a per‑recipient basis.
	The originator's UA conveys his request to the recipient's UA. The recipient's UA automatically issues a non‑recipient notification when any of the following events occur:
1)	the recipient's UA auto–forwards the IP–message to another user;
2)	the recipient's UA discards the IP–message prior to receipt;
3)	the recipient's subscription is terminated before he receives the IP–message.
	Since receipt can occur arbitrarily long after delivery, the recipient's failure to access the IP–message, even for a long period of time (for example, while on an extended business trip), does not constitute non–receipt and thus no notification is issued.
	Note – No legal significance can be adduced from this element of service.
B.49	Non–repudiation of delivery	MT	PR
	This element of service allows the originator of a message to obtain from the recipient(s) of the message irrevocable proof that the message was delivered to the recipient(s). This will protect against any attempt by the recipient(s) to subsequently deny receiving the message or its content. Non–repudiation of delivery is provided to the originator of a message on a per–recipient basis using asymmetric encryption techniques.
B.50	Non–repudiation of origin	MT	PR
	This element of service allows the originator of a message to provide the recipient(s) of the message irrevocable proof of the origin of the message. This will protect against any attempt by the originator to subsequently revoke the message or its content. Non–repudiation of origin is provided to the recipient(s) of a message on a per‑message basis using asymmetric encryption techniques.
B.51	Non–repudiation of submission	MT
	This element of service allows the originator of a message to obtain irrevocable proof that a message was submitted to the MTS for delivery to the originally specified recipient(s). This will protect against any attempt by the MTS to subsequently deny that the message was submitted for delivery to the originally specified recipient(s). Non‑repudiation of submission is provided to the originator of a message on a per–message basis, and uses an asymmetric encryption technique.
B.52	Obsoleting indication	IPM
	This element of service allows the originator to indicate to the recipient that one or more IP–messages he sent previously are obsolete. The IP–message that carries this indication supersedes the obsolete IP–message.
	The action to be taken by the recipient or his IPM UA is a local matter. The intent, however, is to allow the IPM UA or the recipient to, for example, remove or file obsolete messages.
B.53	Ordinary mail	PDPR
	This element of service enables the PDS to transport and deliver the letter produced from the MHS message in the mode available through the ordinary letter mail service in the country of destination. This is the default action for the transport and delivery of a physical message.
B.54	Original encoded information types indication	MT
	This element of service enables an originating UA to specify to the MTS the encoded information types of a message being submitted. When the message is delivered, it also indicates to the recipient UA the encoded information types of the message specified by the originating UA.
B.55	Orinigator indication	IPM
	This element of service allows the identity of the originator to be conveyed to the recipient. The intent of this IPM element of service is to identify the originator in a user–friendly way. In contrast, the MTS provides to the recipient the actual O/R address and directory name, if present, of the originator. DL names should not be used in originator indication.
B.56	Originator requested alternate recipient	MT	PR
	This element of service enables an originating UA to specify, for each intended recipient, one alternate recipient to which the MTS can deliver the message, if delivery to the intended recipient is not possible. The alternate recipient can be a distribution list. For the purposes of determining success or failure (and hence delivery and non‑delivery notifications), delivery to the originator requested alternate recipient is equivalent to delivery to the intended recipient. If the intended recipient has requested redirection of incoming messages, and if the originating UA has requested redirection allowed by the originator, the system first tries to redirect the message. If this fails, the system then attempts to deliver the message to the designated alternate recipient.
B.57	Physical delivery notification by MHS	PD	PR
	This element of service allows an originating user to request that an explicit notification, informing the originator of either successful or unsuccessful delivery of the physical message, be generated and returned by MHS. The notification provides information on delivery but no physical record is provided by the PDS.
	Note 1 – The notification includes the date and time of delivery based on the delivery confirmation given by the delivery person, the addressee or another authorized person. This is subject to national regulations in the destination contry and is also dependent on the type of delivery requested (e.g., in the case of registered mail to addressee in person, the addressee would be the confirming person).
	Note 2 – This notification carries no implication that any action on the part of the recipient (such as examination of the message content) has taken place.
	Note 3 – When this element of service is requested, and the physical message is undeliverable, it is either returned or destroyed depending on national regulations in the destination country, which means that the default action of the element of service B.91 is overridden.
B.58	Physical delivery notification by PDS	PD	PR
	This element of service allows an originating user to request that an explicit notification, informing the originator of either successful or unsuccessful delivery of the physical message, be generated and returned by the PDS. The notification serves as a record of delivery for the originating user to retain for reference.
	Note 1 – The notification includes the date and time, and, in the case of successful delivery, the signature of the person confirming the delivery. The confirming person can be the delivery person, the addressee or another authorized person. This is subject to national regulations in the destination country and is also dependent on the type of delivery requested (e.g., in the case of registered mail to addressee in person, the addressee would be the confirming person).
	Note 2 – This notification carries no implication that any action on the part of the recipient (such as examination of the message content) has taken place.
	Note 3 – When this element of service is requested, and the physical message is undeliverable, is either returned or destroyed depending on national regulations in the destination country, which means that the default action of the element of service B.91 is overridden.
B.59	Physical forwarding allowed	PD	PR
	This element of service enables the PDS to forward the physical message to a forwarding address if the recipient has changed his address and indicated this to the PDS. This is the default action taken by the PDS.
B.60	Physical forwarding prohibited	PD	PR
	This element of service allows an originating user to instruct the PDS not to forward the physical message to a forwarding address.
B.61	Prevention of non–delivery notification	MT	PR
	This element of service enables an originating UA to instruct the MTS not to return a non–delivery notification to the originating UA in the event that the message being submitted is judged undeliverable. In the case of a multi–destination message, the originating UA can request this element of service on a per–recipient basis.
B.62	Primary and copy recipients indication	IPM
	This element of service allows the originator to provide the names of zero or more users, or DLs, who are the intended primary recipients of the IP–message, and the names of zero or more users, or DLs, who are the intended copy recipients of the IP–message. It is intended to enable a recipient to determine the category in which each of the specified recipients (including the recipient himself) was placed. The exact distinction between these two categories of recipients is unspecified. However, the primary recipients, for example, might be expected to act upon the IP‑message, while the copy recipients might be sent the IP–message for information only.
	Note – As an example of this element of service in a typical memorandum, the primary recipients are normally designated by the directive “to:” while “cc:” identifies the copy recipients.
B.63	Probe	MT
	This element of service enables a UA to establish before submission whether a particular message could be delivered. The MTS provides the submission information and generates delivery and/or non–delivery notifications indicating whether a message with the same submission information could be delivered to the specified recipient UAs.
	The probe element of service includes the capability of checking whether the content size, content type, and/or encoded information types would render it undeliverable. The significance of the result of a probe depends upon the recipient UA(s) having registered with the MTS the encoded information types, content type and maximum message size that it can accept. This element of service is subject to the same delivery time targets as for the urgent class. In the case of DLs, a probe indicates nothing about the likelihood of successful delivery to the DL members, but only whether the originator has the right to submit to the DL.
B.64	Probe origin authentication	MT
	This element of service allows the originator of a probe to provide to any MTA through which the probe is transferred a means to authenticate the origin of the probe (i.e. a signature). Probe origin authentication is on a per–probe basis, and uses an asymmetric encryption technique.
B.65	Proof of delivery	MT	PR
	This element of service allows the originator of a message to obtain from the recipient(s) of the message the means to authenticate the identity of the recipient(s) and the delivered message and content. Message recipient authentication is provided to the originator of a message on a per–recipient basis using either symmetric or asymmetric encryption techniques.
B.66	Proof of submission	MT
	This element of service allows the originator of a message to obtain from the MTS the means to authenticate that the message was submitted for delivery to the originally intended recipient. Message submission authentication is provided on a per–message basis, and can use symmetric or asymmetric encryption techniques.
B.67	Receipt notification request indication	IPM	PR
	This element of service allows the originator to ask that he be notified when the IP–message being sent is received. In the case of a multi–recipient message, the originator can request this element of service on a per‑recipient basis. This element of service also implicitly requests non–receipt notification request indication.
	The originator's UA conveys his request to the recipient's UA. The recipient can instruct his UA to honour such requests, either automatically (for example, when it first renders the IP–message on the recipient's terminal) or upon his explicit command. The recipient can also instruct his UA, either in blanket fashion or case by case, to ignore such requests.
B.68	Redirection disallowed by originator	MT
	This element of service enables an originating UA to instruct the MTS, if the recipient has requested the redirection of incoming messages element of service, that redirection should not be applied to a particular submitted message.
B.69	Redirection of incoming messages	MT
	This element of service enables a UA to instruct the MTS to redirect incoming messages addressed to it, to another UA or to a DL, for a specified period of time, or until revoked.
	Note 1 – This is an MT element of service that does not necessitate delivery to the intended recipient before redirection can take place. It is therefore distinct from the IPM Auto–Forwarded Indication Element of Service.
	Note 2 – When security provisions are in force, different incoming messages, on the basis of their security labels, may be redirected to separate alternate recipients or not re–directed at all.
B.70	Registered mail	PD	PR
	This element of service allows an originating user to instruct the PDS to handle the physical message as registered mail.
B.71	Registered mail to addressee in person	PD	PR
	This element of service allows an originating user to instruct the PDS to handle the physical message as registered mail and to deliver it to the addressee only.
B.72	Reply request indication	IPM	PR
	This element of service allows the originator to request that a recipient send an IP–message in reply to the IP‑message that carries the request. The originator can also specify the date by which any reply should be sent, and the one or more users and DLs to whom the originator requests (but does not demand) be among the preferred recipients of any reply. The recipient is informed of the date and names but it is up to the recipient to decide whether or not, and if so, to whom to reply.
	Note – A blind copy recipient should consider carefully to whom he sends a reply, in order that the meaning of the blind copy recipient indication element of service is preserved.
B.73	Replying IP–message indication	IPM
	This element of service allows the originator of an IP–message to indicate to the recipient(s) that this IP‑message is being sent in reply to another IP–message. A reply can, depending on the wishes of the originator of the replied–to message, and the final decision of the originator of the reply, be sent to:
1)	the recipients specified in the reply request indication of the replied–to message;
2)	the originator of the replied–to message;
3)	the originator and other recipients;
4)	a distribution list, in which the originator of the replied–to message can be a receiving member;
5)	other recipients as chosen by the originator of the reply.
	The recipients of the reply receive it as a regular IP–message, together with an indication of which IP‑message it is a reply to.
B.74	Report origin authentication	MT
	This element of service allows the originator of a message (or probe) to authenticate the origin of a report on the delivery or non–delivery of the subject message (or probe), (a signature). Report origin authentication is on a per‑basis, and uses an asymmetric encryption technique.
B.75	Request for forwarding address	PD	PR
	This element of service allows an originating user to instruct the PDS to provide the forwarding address if the recipient has changed his address and indicated this to the PDS.
	This element of service can be used with either physical forwarding allowed or prohibited. The provision of the forwarding address by the PDS to an originating user is subject to national regulations in the destination country. The default action is no provision of the forwarding address.
B.76	Requested delivery method	MT	PR
	This element of service allows a user to request, on a per–recipient basis, the preference of method or methods of message delivery (such as through an access unit). Non–delivery results if preference(s) cannot be satisfied.
B.77	Restricted delivery	MT
	This element of service enables a recipient UA to indicate to the MTS that it is not prepared to accept delivery of messages from certain originating UAs or DLs.
	Note 1 – This element of service can be requested in either of two ways:
a)	specification by the recipient UA of unauthorized originators, all other originators are considered as authorized;
b)	specification by the recipient UA of authorized originators, all other originators are considered to be unauthorized.
	Note 2 – The MTS abstract service specified in Rec. X.411 does not provide a technical realization of this element of service. Its provision may be the subject of further standardization.
B.78	Return of content	MT
	This element of service enables an originating UA to request that the content of a submitted message be returned with any non–delivery notification. This will not be done, however, if any encoded information type conversion has been performed on the message's content.
B.79	Secure access management	MT
	This element of service enables an MTS user to establish an association with the MTS, or the MTS to establish an association with an MTS user, or an MTA to establish an association with another MTA. It also establishes the strong credentials of the objects to interact, and the context and security–context of the association. Secure access management can use either an asymmetric or a symmetric encryption technique. When access security is achieved through strong credentials, they can be periodically updated.
B.80	Sensitivity indication	IPM
	This element of service allows the originator of an IP–message to specify guidelines for the relative sensitivity of the message upon its receipt. It is the intent that the sensitivity indication should control such items as:
1)	whether the recipient should have to prove his identity to receive the IP–message;
2)	whether the IP–message should be allowed to be printed on a shared printer;
3)	whether an IPM UA should allow the recipient to forward the received IP–message;
4)	whether the IP–message should be allowed to be auto–forwarded.
	The sensitivity indication can be indicated to the recipient or interpreted directly by the recipient's IPM UA.
	If no sensitivity level is indicated, it should be assumed that the IP–message originator has advised no restriction on the recipient's further disposition of the IP–message. The recipient is free to forward, print, or otherwise do as he chooses with the IP–message.
	Three specific levels of sensitivity above the default are defined:
–	Personal: The IP–message is sent to the recipient as an individual, rather than to him in his role. There is no implication that the IP–message is private, however.
–	Private: The IP–message contains information that should be seen (or heard) only by the recipient, and not by anyone else. The recipient's IPM UA can provide services to enforce this intent on behalf of the IP–message originator.
–	Company–confidential: The IP–message contains information that should be treated according to company–specific procedures.
B.81	Special delivery	PD	PR
	This element of service allows an originating user to instruct the PDS to transport the letter produced form the MHS message through the ordinary letter mail circulation system and to deliver it by special messenger delivery.
B.82	Stored message alert	MS
	This element of service allows a user of an MS to register relevant sets of criteria that can cause an alert to be generated to the user when a message arrives at the MS satisfying the selected criteria. The generation of the alert can occur as follows:
1)	if the UA is connected and on–line to the MS, the alert message will be sent to the UA as soon as a message arrives at the MS that safisfies the registered criteria for generating alerts. If the UA is off line then the next time the UA connects to his MS after a message arrives at the MS satisfying the registered criteria, the user will be informed that one or more alert cases have occurred, the details of which can be determined by performing a Stored Message Summary;
2)	in addition to, or as an alternative to 1) above, the MS can use other mechanisms to inform the user.
B.83	Stored message auto–forward	MS
	This element of service allows a user of an MS to register requests that the MS auto–forward selected messages that are delivered to it. The user of the MS can select through registration several sets of criteria chosen from the attributes available in the MS, and messages meeting each set of criteria will be auto–forwarded to one or more users or DLs. One text per selection criteria can also be specified to be included with each auto–forwarded message.
B.84	Stored message deletion	MS
	This element of service enables a recipient UA to delete certain of its messages from the MS. Messages cannot be deleted if they have not been previously listed.
B.85	Stored message fetching	MS
	This element of service enables a recipient UA to fetch from the MS a message, or portions of a message. The UA can fetch a message (or message portion) based on the same search criteria that can be used for stored message listing.
B.86	Stored message listing	MS
	This element of service provides a recipient UA with a list of information about certain of its messages stored in the MS. The information comprises selected attributes from a message's envelope and content and others added by the MS. The UA can limit the number of messages that will be listed.
B.87	Stored message summary	MS
	This element of service provides a recipient UA with a count of the number of messages satisfying a specified criteria based on one or more attributes of the message stored in the MS.
B.88	Subject indication	IPM
	This element of service allows the originator to indicate to the recipient(s) the subject of an IP–message being sent. The subject information is to be made available to the recipient.
B.89	Submission time stamp indication	MT
	This element of service enables the MTS to indicate to the originating UA and each recipient UA the date and time at which a message was submitted to the MTS. In the case of physical delivery, this element of service also enables the PDAU to indicate the date and time of submission on the physical message.
B.90	Typed body	IPM
	This element of service permits the nature and attributes of the body of the IP–message to be conveyed along with the body. Because the body can undergo conversion, the body type can change over time.
B.91	Undeliverable mail with return of physical message	PD	PR
	This element of service enables the PDS to return the physical message without delay, with reason indicated to the originator, if it cannot be delivered to the addressee. This is the default action to be taken by the PDS.
	Note – In the case of “poste restante” the return of the physical message will take place after some period of time.
B.92	Use of distribution list	MT	PR
	This element of service enables an originating UA to specify a distribution list in place of all the individual recipients (users or nested LDs) mentioned therein. The MTS will add the members of the list to the recipients of the message and send it to those members. Distribution lists can be members of distribution lists, in which case the list of recipients can be successively expanded at several places in the MTS.
B.93	User/UA capabilities registration	MT
	This element of service enables a UA to indicate to its MTA, through registration, the unrestricted use of any or all of the following capabilities with respect to received messages:
1)	the content type(s) of messages it is willing to have delivered to it;
2)	the maximum content length of a message it is willing to have delivered to it;
3)	the encoded information type(s) of messages it is willing to have delivered to it.
	The MTA will not deliver to a UA a message that does not match, or exceeds, the capabilities registered.
ANNEX C
(to Recommendation X.400)
Elements of service modifications with respect to the 1984 version
C.1	New elements of service in 1988 (see Table C–1/X.400)
TABLE C–1/X.400
Elements of service	MT	IPM	PD	MS	Annex B Ref.	
Additional physical rendition			X		B.2 	
Basic physical rendition			X		B.7 	
Content confidentiality	X				B.10	
Content integrity	X				B.11	
Conversion prohibition in case of loss of information	X				B.14	
Counter collection			X		B.16	
Counter collection with advice			X		B.17	
Delivery via Bureaufax service			X		B.23	
Designation of recipient by directory name	X				B.24	
DL expansion history indication	X				B.26	
DL expansion prohibited	X				B.27	
EMS (express mail service)			X		B.28	
Incomplete copy indication		X			B.36	
Language indication		X			B.38	
Latest delivery designation	X				B.39	
Message flow confidentiality	X				B.40	
Message origin authentication	X				B.42	
Message security labelling	X				B.43	
Message sequence integrity	X				B.44	
Non–repudiation of delivery	X				B.49	
Non–repudiation of origin	X				B.50	
Non–repudiation of submission	X				B.51	
Ordinary mail			X		B.53	
Originator requested alternate recipient	X				B.56	
Physical delivery notification by MHS			X		B.57	
Physical delivery notification by PDS			X		B.58	
Physical forwarding allowed			X		B.59	
Physical forwarding prohibited			X		B.60	
Probe origin authentication	X				B.64	
Proof of delivery	X				B.65	
Proof of submission	X				B.66	
Redirection d is allowed by originator	X				B.68	
Redirection of incoming messages	X				B.69	
Registered mail			X		B.70	
Registered mail to addressee in person			X		B.71	
Report origin authentication	X				B.74	
Request for forwarding address			X		B.75	
Requested delivery method	X				B.76	
Restricted delivery	X				B.77	
Secure access management	X				B.79	
Special delivery			X		B.81	
Stored message alert				X	 B.82	
Stored message auto–forward				X	 B.83	
Stored message deletion				X	 B.84	
Stored message fetching				X	 B.85	
Stored message listing				X	 B.86	
Stored message summary				X	 B.87	
Undeliverable mail with return of physical message			X		B.91	
Use of distribution list	X				B.92	
User/UA capabilities registration	X				B.93	
C.2	Mapping of the 1984 and 1988 elements of service tables (see Figure C–1/X.400)
Figure C–1/X.400 CCITT - 0706820-89

C.3	Classification of new elements of service
	The new elements of service that were added to the 1984 X.400–Series to create the 1988 F.400/X.400–Series Recommendations are all classified as additional optional user facilities with the following exceptions:

C.3.1	MT service
–	DL expansion history indication;
–	requested delivery method.
C.3.2	IPM service
–	DL expansion history indication;
–	language indication;
–	requested delivery method.
C.3.3	MH/PD service intercommunication
	Although some of the elements of service used in this intercommunication are classified as Base (see X.400, § 19.4), and some are classified as essential optional user facilities (see X.400, § 19.5), the provision of MH/PD service intercommunication is an option itself. When this intercommunication is provided, the base elements of service and optional user facilities shall be supported as classified in this Recommendation.
C.3.4	Message store
	Although some of the elements of service used with the message store are classified as Base (see X.400, § 19.6), and others are classified as essential optional user facilities (see X.400, § 19.7), the provision of a message store is itself an option, and therefore the classifications are applicable only for the provider of a message store.
C.4	Changes in classification of 1984 elements of service
	All the elements of service in 1984 have retained their 1984 classifications with the following exception:
	–	Non–receipt notification request.
C.4.1	Miscellaneous changes
	The element of service registered encoded information types in 1984 is now called user/UA capabilities registration and it has been extended in functionality.
	Some of the 1984 element of service definitions have been revised editorially for ease of reading.
ANNEX D
(to Recommendation X.400)
Differences between CCITT Recommendation X.400
and ISO Standard 10021–1
(This Annex is not a part of this Recommendation)
	This Annex points out the major differences between this Recommendation and the corresponding ISO International Standard. Because the differences in many cases involve the inclusion or exclusion of a word, a phrase, or a sentence, and these occur in many places throughout the text, this Annex does not specifically point to these instances. Rather it summarizes the intent of these differences.
	The following are the major differences:
1)	The CCITT text makes references throughout to CCITT services and their relationship to MHS;
2)	Figure 5/X.400 showing relationships between management domains and corresponding notes;
3)	Roles of ADMD and PRMD in naming;
4)	Use of MHS in provision of public services (§ 17);
5)	The note about responsibility for storing deferred delivery messages (Annex B, § B.19) is not included in the ISO text.