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Applications LEMONADE Working Group This document specifies the architecture for mobile email, as described by the OMA, using Internet Mail protocols. This architecture is the basis of the work of the LEMONADE WG and is a guideline for the LEMONADE Profile.

This document describes the architecture of OMA mobile email (MEM) using Internet Mail protocols defined by the IETF. The LEMONADE work group has enhanced many of these protocols for use in the mobile environment and are summarized in the LEMONADE profile and its revision LEMONADE profile bis . This document shows how the OMA MEM Requirement document , OMA MEM Architecture , and OMA MEM Technical Specification relate to the work of LEMONADE.

The OMA Mobile Email (MEM) sub-working group has spent some time studying the requirements and architecture of mobile email. IETF LEMONADE has been liaising with them and has based much of our Internet Mail enhancements based on their input. This section summarizes the output of the OMA.

The OMA MEM activity collected a set of use cases and derived requirements for a mobile email enabler (MEM). The OMA MEM Requirements summarizes this work. Some requirements relates to email protocols, some involve other OMA technologies outside the scope of IETF and some relate to implementations and normative interoperability statements for clients and servers.

This section introduces the OMA MEM Architecture.

The OMA MEM activity has derived a logical architecture from the requirements and use cases described in . A simplification for illustrative purposes is shown in , where arrows indicate content flows.

| MEM | I2 | Email | |Client| ME-2| Server |<---->| Server | |______|<--------|________| |________| ^ |ME-5 | ]]>

identifies the following elements: The MEM client that implements the client-side functionality of the OMA Mobile Email Enabler. It is also responsible for providing the mobile email user experience and interface to the user and storing the email and data to be sent to the MEM server when not connected. The MEM server that implements the server-side functionality of the OMA Mobile Email Enabler (MEM). The MEM protocol between the MEM Client and MEM Server. It is responsible for all the in-band data exchanges that take place between the MEM client and server in order to update the MEM client with email server changes, the email server with changes in the MEM client and to send new email from the email server. Other OMA enablers are needed to directly support the mobile email enabler. They are out of scope of IETF but they may include support for: Client provisioning and management for over the air installation of the MEM client on the device, provisioning of its settings and revocation, Messaging enablers for out-of-band notification, where out-of-band notifications that are server to client event exchanges not transported by the MEM protocol but via other channels, and Billing, charging, and so on. OMA identifies different interfaces: ME-1: MEM client interface to interact via the MEM protocol with the MEM server ME-2: Corresponding interface of the MEM server ME-3: Out-of-band MEM server interfaces, for example to support generation of server to client notifications. ME-4: Out-of-band MEM client interfaces (e.g. to receive server to client notifications). ME-5: Interface for management of MEM enabler server settings, user preferences, and filters, globally and per account. The MEM server enables an email server. In a particular implementation, the email server may be packaged with (internal to it) the MEM server or be a separate component. In such cases, interfaces to the email server are out of scope of the OMA MEM specifications. In the present document, we focus on the case where the backend consists of IETF IMAP and Submit servers. However, we also discuss the relationship to other cases. The I2 interface is an OMA notation to designate protocol / interfaces that are not specified by the MEM enabler but may be standardized elsewhere.

The OMA MEM Architecture document further identifies deployment models.

The OMA MEM Architecture document identifies OMA MEM server proxies as server components that may be deployed ahead of firewalls to facilitate firewall traversal.

OMA MEM identifies that each component (MEM client, MEM servers, other enablers, and the email server) may be deployed in different domains, possibly separated by firewalls and other network intermediaries. MEM proxies may be involved in front of firewall that protects the MEM server domain. OMA MEM targets support of configurations where: All components are within the same domain, such as in a mobile operator MEM client and other enablers are in the mobile operator domain, there is a MEM proxy, and the MEM server and email server are in the domain of the email service provider MEM client and other enablers as well as a MEM proxy are in the mobile operator domain, MEM server and email server are in the domain of the email service provider MEM client and other enablers are in the mobile operator domain, a MEM proxy is in a third party service provider domain and MEM server and email server are in the domain of the email service provider MEM client, other enabler and MEM server are in the mobile operator domain and email server is in the domain of the email service provider MEM client and other enablers are in the mobile operator domain, MEM server is in a third party service provider domain and the email server is in the domain of the email service provider The e-mail service provider can be either a third-party service provider, a network service provider, or an enterprise e-mail service.

The OMA MEM activity will conclude with a specification for a mobile email enabler (MEM). The ongoing work is in OMA MEM Technical Specification . LEMONADE is a basis for the mechanism. However, some additional details that are outside the scope of IETF will also be included. OMA provides ways to perform provisioning via OMA client provisioning and device management. Other provisioning specifications are available (e.g., SMS based). OMA provides enablers to support out-of-band notification mechanisms, as well as filter specifications (such as XDM), remote device deactivation, and other, non-Internet activities.

This section introduces the LEMONADE Architecture. The IETF LEMONADE activity has derived a LEMONADE profile with the logical architecture represented in , where arrows indicate content flows.

| IMAP |<---------------| MTA | | MUA |- | Store | |_____| |_____| \ |__________| \ | \ |URLAUTH \SUBMIT | \ ____v_____ \ | | _____ \ | LEMONADE | ESMTP | | ---->| Submit |--------------->| MTA | | Server | |_____| |__________| ]]>

The LEMONADE profile assumes: IMAP protocol including LEMONADE profile extensions SUBMIT protocol, including LEMONADE profile extensions LEMONADE profile compliant IMAP store connected to MTA (Mail Transfer Agent) via ESMTP LEMONADE profile compliant Submit server connected to an MTA, often via ESMTP Out-of-band server to client notifications relying on external notification mechanisms (and notification protocols) that may be out of scope of the LEMONADE profile. A LEMONADE aware MUA (Mail User Agent). While use of out-of-band notification is described in the LEMONADE profile, support for the underlying notifications mechanisms/protocols is out of scope of the LEMONADE specifications. Further details on the IETF email protocol stack and architecture can be found in

illustrates the mapping of the IETF LEMONADE logical architecture on the OMA MEM logical architecture.

| IMAP |<-----------| MTA | || MUA || ME-2a | | Store | | |_____| ||_____||\ME-1 | |__________| | | MEM | \ | | | | Client| \ | |URLAUTH | |_______| \SUBMIT | | \ | ____v_____ | \ | | | | _____ \ | | LEMONADE | | ESMTP | | ---->| Submit |----------->| MTA | ME-2b | | Server | | |_____| | |__________| | |MEM Email | |Server Server| |_________________| ^ |ME-5 | ]]>

As described in , the LEMONADE profile assumes LEMONADE profile compliant IMAP stores and Submit servers. Because the LEMONADE profile extends the IMAP store and the submit server, the mobile enablement of email provided by the LEMONADE profile is directly provided in these servers. Mapping to the OMA MEM logical architecture, for the case considered and specified by the LEMONADE profile, we logically combine the MEM server and email server. However, in lemonade we split them logically into a distinct LEMONADE message store and a LEMONADE submit server. ME-2 consists of two interfaces. ME-2a is IMAP extended according to the LEMONADE profile. ME-2b is SUBMIT extended according to the LEMONADE profile. The MUA is part of the MEM client. The external notifications mechanism is part of OMA enablers specified by the OMA.

The OMA MEM activity is not limited to enabling Lemonade compliant servers. It explicitly identifies the need to support other back-ends. This is, of course, outside the scope of the IETF Lemonade activity.

illustrates the case of IMAP servers that are not LEMONADE compliant. In such case, the I2 interface between the MEM server components and the IMAP store and submit server are IMAP and SUBMIT without Lemonade extensions.

|Enabler |<------>|IMAP |<----->| MTA | | MUA |\ ME-2a | Server | |Store | |_____| |_____| \ |__________| |_____________| \ | \ |URLAUTH \SUBMIT | \ ____v_____ _____________ \ | | | | _____ \ | LEMONADE | SUBMIT |NON-LEMONADE | ESMTP | | -->| MEM | |Submit | | | | Enabler |------->|Server |------>| MTA | ME-2b | Server | | | |_____| |__________| |_____________| ]]>

illustrates the cases where the message store and submit servers are not IMAP store or submit servers. They may be POP3 servers or other proprietary message stores.

|Enabler |<------>|Message |<----->| MTA | | MUA |\ ME-2a | Server | |Store | |_____| |_____| \ |__________| |_____________| \ | \ |URLAUTH \SUBMIT | \ ____v_____ _____________ \ | | | | _____ \ | LEMONADE | I2 |Proprietary | ESMTP | | -->| MEM | |Submit | | | | Enabler |------->|Server |------>| MTA | ME-2b | Server | | | |_____| |__________| |_____________| ]]>

I2 designates proprietary adapters to the back-ends.

OMA MEM RD and AD emphasize the need to provide mechanisms for server to client notifications of email events and filtering. illustrates how notification and filtering works in the LEMONADE profile.

|NF|____ | | | ---- | _____ __v__| IMAP |__ LEMONADE |___ ESMTP __| | | |<-------->|VF| IMAP |DF |<--------|AF| MTA | | MUA |\ ME-2a |-- Store |--- --|_____| |_____| \ |_____________| ^ \_\_______________|_______| \ |URLAUTH \SUBMIT | \ ____v_____ \ | | _____ \ | LEMONADE | ESMTP | | ---->| Submit |--------------->| MTA | ME-2b | Server | |_____| |__________| ]]>

In , we define four categories of filters: AF: Administrative Filters - The e-mail service provider usually sets administrative filters. The user typically does not configure AF. AF applies policies covering content filtering, virus protection, spam filtering, etc. DF: Deposit Filters - Filters that are executed on deposit of new emails. They can be defined as SIEVE filters. They can include vacation notices. VF: View Filters - Filters that define which emails are visible to the MUA. View filters can be performed via IMAP using the facilities described in . NF: Notification Filters - Filters that define for what email server event an out-of-band notification is sent to the client, as described in . The MUA can manage the NF and DF filters using the SIEVE management protocol.

We note there are security risks associated with: Out-of-band notifications Server configuration by client Client configuration by server Presence of MEM proxy servers Presence of MEM servers as intermediaries Measures to address the need to traverse firewalls We refer the reader to the relevant Internet Mail, IMAP, SUBMIT, and Lemonade documents for how we address these issues.

None.

The authors acknowledge and appreciate the work and comments of the IETF LEMONADE working group and the OMA MEM working group. We extracted the contents of this document from sections of draft-ietf-lemonade-profile-bis-05.txt by Stephane Maes, Alexey Melnikov and Dave Cridland, as well as sections of draft-ietf-lemonade-notifications-04.txt by Stephane Maes and Ray Cromwell.

Open Mobile Alliance Open Mobile Alliance Open Mobile Alliance This document describes a profile (a set of required extensions, restrictions, and usage modes) of the IMAP and mail submission protocols. This profile allows clients (especially those that are constrained in memory, bandwidth, processing power, or other areas) to efficiently use IMAP and Submission to access and submit mail. This includes the ability to forward received mail without needing to download and upload the mail, to optimize submission, and to efficiently resynchronize in case of loss of connectivity with the server.</t><t> The Internet Email to Support Diverse Service Environments (Lemonade) profile relies upon extensions to IMAP and Mail Submission protocols; specifically, the URLAUTH and CATENATE IMAP protocol (RFC 3501) extensions and the BURL extension to the SUBMIT protocol (RFC 4409). [STANDARDS TRACK] This document describes a profile (a set of required extensions, restrictions and usage modes) of the IMAP and mail submission protocols. This profile allows clients (especially those that are constrained in memory, bandwidth, processing power, or other areas) to efficiently use IMAP and Submission to access and submit mail. This includes the ability to forward received mail without needing to download and upload the mail, to optimize submission and to efficiently resynchronize in case of loss of connectivity with the server. The Lemonade profile relies upon several extensions to IMAP and Mail Submission protocols. The Internet Message Access Protocol, Version 4rev1 (IMAP4rev1) allows a client to access and manipulate electronic mail messages on a server. IMAP4rev1 permits manipulation of mailboxes (remote message folders) in a way that is functionally equivalent to local folders. IMAP4rev1 also provides the capability for an offline client to resynchronize with the server. IMAP4rev1 includes operations for creating, deleting, and renaming mailboxes, checking for new messages, permanently removing messages, setting and clearing flags, RFC 2822 and RFC 2045 parsing, searching, and selective fetching of message attributes, texts, and portions thereof. Messages in IMAP4rev1 are accessed by the use of numbers. These numbers are either message sequence numbers or unique identifiers. IMAP4rev1 supports a single server. A mechanism for accessing configuration information to support multiple IMAP4rev1 servers is discussed in RFC 2244. IMAP4rev1 does not specify a means of posting mail; this function is handled by a mail transfer protocol such as RFC 2821. [STANDARDS TRACK] This document is a self-contained specification of the basic protocol for the Internet electronic mail transport. [STANDARDS TRACK] This memo splits message submission from message relay, allowing each service to operate according to its own rules (for security, policy, etc.), and specifies what actions are to be taken by a submission server.</t><t> Message relay and final delivery are unaffected, and continue to use SMTP over port 25.</t><t> When conforming to this document, message submission uses the protocol specified here, normally over port 587.</t><t> This separation of function offers a number of benefits, including the ability to apply specific security or policy requirements. [STANDARDS TRACK] This document describes an extension to the Sieve email filtering language for an autoresponder similar to that of the Unix "vacation" command for replying to messages. Various safety features are included to prevent problems such as message loops. [STANDARDS TRACK]

This document discusses how to provide notification and filtering mechanisms to mail stores to meet Lemonade goals. This document also discusses the use of server to server notifications, and how server to server notifications fit into an architecture which provides server to client notifications. Gellens [page 1] Expires January 2009 Internet Draft Lemonade Notifications Architecture July 2008 Over its thirty-five year history Internet Mail has undergone significant changes in scale and complexity, as it has become a global infrastructure service. The first standardized architecture for networked email specified little more than a simple split between the user world and the transmission world. Core aspects of the service, such as the styles of mailbox address and basic message format, have remained remarkably constant. However today's Internet Mail is distinguished by many independent operators, many different components for providing service to users and many others for performing message transfer. Public discussion of the service often lacks common terminology and a common frame of reference for these components and their activities. Having a common reference model and terminology facilitates discussion about problems with the service, changes in policy, or enhancement to the service's functionality. This document offers an enhanced Internet Mail architecture that targets description of the existing service, in order to facilitate clearer and more efficient technical, operations and policy discussions about email. Sieve scripts allow users to filter incoming email. Message stores are commonly sealed servers so users cannot log into them, yet users must be able to update their scripts on them. This document describes a protocol "ManageSieve" for securely managing Sieve scripts on a remote server. This protocol allows a user to have multiple scripts, and also alerts a user to syntactically flawed scripts.