<abstract>This specification defines an XMPP protocol extension for message receipts, whereby the sender of a message can request notification that it has been received by the intended recipient.</abstract>
<remark><p>Relaxed the business rules to allow inclusion of receipt requests even to the bare JID and even if the sender does not yet know whether the intended recipient supports this protocol; clarified the level of reliability that this protocol does and does not provide; provided explicit recommendations about when and when not to request receipts; removed text about XEP-0155 negotiation.</p></remark>
<remark><p>Added two more scenarios; defined business rule about not sending to bare JIDs; specified security consideration regarding presence leaks.</p></remark>
<remark><p>Added text and examples for service discovery; added text and examples for chat session negotiation; added recommendations regarding message processing, retries, etc.</p></remark>
<p>While &xep0079; provides message acknowledgements at the server level, it does not extend that model all the way to the client. However, sometimes client-level acknowledgements are needed, for example to provide "receipts". This document defines a mechanism for XMPP message receipts, which are functionally equivalent to the "delivered" or "displayed" event in &xep0022;, which this specification in part obsoletes. <note>This specification does not distinguish between delivery and presentation, as was done in the message events protocol, in part because no existing clients make the distinction.</note></p>
<p>Note: This extension is functionally equivalent to an <cite>Advanced Message Processing</cite> rule of "receipt" but uses a dedicated namespace to simplify processing by end user clients and intermediate routers.</p>
<p>This document defines a protocol that enables a sender to ask the recipient to return a receipt for a message. Although the return of a message receipt lets the sender know that the message has been delivered, there are many reasons why the sender might not receive a receipt immediately or at all, including but not limited to the following:</p>
<li>The sender addressed the message to the recipient's bare JID &LOCALBARE; and therefore does not know if the recipient even supports message receipts.</li>
<li>The sender has not bothered to determine whether the recipient supports message receipts.</li>
<li>The recipient (or the particular intended resource to which the sender addressed the message) does not in fact support message receipts.</li>
<li>The intended resource supports message receipts but the recipient's server delivers the message to another resource that does not support message receipts.</li>
<li>The recipient's client receives the message but experiences a malfunction before generating a receipt.</li>
<li>The recipient returns a receipt but the receipt is lost on the way back from the recipient to the sender (e.g., because of connectivity issues or software failures at any hop).</li>
<p>As a result, this document does not define a protocol for complete reliability or guaranteed delivery, and those who implement and deploy this protocol need to be aware of its limitations, as described throughout this specification.</p>
<p>Note: Message receipts can be combined with the rules specified in <cite>Advanced Message Processing</cite> (e.g., the deliver rule) for more complete reporting.</p>
<p>If an entity supports message receipts, it MUST report that by including a &xep0030; feature of "urn:xmpp:receipts" in response to disco#info requests:</p>
<examplecaption="Initial Service Discovery information request"><