PRECEDENCE RULES IN ELECTRONIC MESSAGING SERVERS

Abstract: According to the present invention, precedence rules that govern the granting of user level services for a domain are disclosed. In one aspect of the invention, a method of granting a requested service based upon a precedence rule is disclosed. As a method, a request for the user level service is received (604) after which it is determined if the requested user level service is a member of a proper subset of the allowed domain level services (612). If the requested user level service is determined to be a proper subset of the set of allowed domain level services, then the requested user level service is granted (616). In so doing, the granted user level service becomes a member of the proper subset of the set of allowed domain level services.

Description: PRECEDENCE RlJLES IN ELECTRONIC MESSAGING SERVERS PRECEDENCE RULES IN ELECTRONIC MESSAGING SERVERS FIELD OF THE INVENTION The present invention relates in general to client/server data communication systems and, more particularly, to a mail server included in an electronic mail system for use within a client/server data processing system. More particularly still, the present invention is directed towards a method and apparatus for defining a virtual domain in an email system. BACKGROUND OF THE INVENTION Computer systems are well known in the art and have become a business staple and are also found in many homes. One feature available to the business world is that of using electronic mailing (email) to send and receive messages and other information to and from one another in a business setting. Similarly, home computers, such as desk tops or laptops, and other information devices, such as personal digital assistants (PDAs), allow telecommuting such that a user can connect to the user's work server and down load and upload messages. The email system allows clients of a network system, which is maintained by a server system, to send messages or data from one user to another. In order to minimize disk space and requirements as well as to maximize functionality and consistency of the electronic mailing engine used in the network system, the engine is typically located on the server and is merel accessed by a client in order to send messages or retrieve messages to or from another user or client on the server system. In this way, the client system typically allows the user to perform such operations as composing, updating, and sending messages while the server in such a system provides, in part, a server based message repository as well as providing message transmission and reception functions for the user at the client level. A traditional email system 100, configured to operate in what is referred to as a consumer host mode, is illustrated in Fig. 1. The email system 100 includes a number of consumers and/or businesses 102-1 ("abc.com") through 102-n ("xyz.gov") each of which is coupled to a service provider (SP) 104 ("isp.net"). Traditionally, the service provider (SP) 104 provides the various consumers and/or businesses 102 with just an unprotected IP router. The consumers and/or businesses 102 also operate and maintain their own application servers, including the email server, DNS server, and (if needed) LDAP server (not shown). For their own protection, each of the consumers and/or businesses 102 must operate through a firewall that filters out undesirable packets and insulates the organization's internal network from the Internet. Notice that for many organizations, especially small ones, the email server may actually be the firewall system. In the email system 100, those consumers and/or businesses 102-1 through 102-n who wish to read their mail must be connected to a service provider (SP) email server 106. The SP 106 also operates an email mailbox 108, and a DNS server 110 that provides the following services, a primary master server for the SP's own domain (ISP.net), to designate as the root server for all consumers and/or businesses, act as a primary master server for consumers and/or businesses who do not wish to maintain their own public DNS server, and as a secondary server for consumers and/or businesses who prefer to maintain their own public server. As part of the services provided by the SP 106, an SMTP relay host 112 that is managed by the SP offers offer a number of value added services, for which the SP may charge additional fees. In some cases, the relay host can be configured to allow the relay host to accept and hold the consumer's email when their mail server is down. However, unfortunately, the relay host imposes a significant management burden on the SP since in some cases, consumer email may live on this server for an indefinite time raising issues of backup and failure recovery. If one of the consumer servers fails because of being swamped, for example, then the consumer's email may roll over to the SP's relay host. Because of this, most SPs do not offer a relay host for those consumers and/or businesses that are hosting their own email server. The SP also provides a directory service in the form of the LDAP Directory server that is located at the consumer's site, which can be operated by the consumer. In this way, most organizations do not expose their LDAP servers to the public network for security reasons. In the example shown in Fig. 1, a mail user in ABC, Inc. (which lawfully owns its DNS domain name abc.cbm, but relies on the ISP isp.net to host its email) desiring to send and receive mail uses the domain name username(α).abc.com even though his mailserver is really mailhost.isp.net. It also means that any user in the abc.com domain, connects to a mailhost in the domain abc.com - for example mail.abc.com - to access his/her mail. Since the email system 100 requires a separate mail server to be supported by the SP 106 for each of the domains abc.com through xyz.gov, although well understood and easy to manage, the email system 100 is not cost effective for small domains. In addition, as the number of domains increases, the management of the individual services becomes increasingly unwieldy. Internet service providers (ISPs) have a growing interest in hosting email services for always larger and more numerous organizations. Many businesses see the ability to farm out email services as a very attractive cost- saving idea. It is therefore desirable that an email service provider be able to offer email services to multiple organizations each of which has their own virtual domain and to support the ability to define such domains in the directory and host them on a shared mail server. Thus, an email architecture that can support a single mail server which, in turn, can support many different domains associated with consumers and/or businesses is desirable. However, when the users within a domain are granted a particular set of user level services, that set of user level services must be a proper subset of the associated allowed set of domain services. Therefore, what is desired is a set of precedence rules that govern the granting of user level for a particular domain having a set of domain services. SUMMARY OF THE INVENTION To achieve the foregoing, and in accordance with the purpose of the present invention, methods for granting a user level service based upon a set of allowed domain level services is provided. In accordance with one aspect of the present invention, a method is disclosed where a requested user level service is granted or not based upon a set of allowed domain level services. The user level service is requested and a subsequent determination is made whether or not the requested user level service is a member of a proper subset of the set of allowed domain level services. If the requested service is determined to be a member of the proper subset of allowed domain level services, then the requested user level service is granted. In so doing, the granted user level services become a member of a set of allowed user level services. BRIEF DESCRIPTION OF THE DRAWINGS The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which: Fig. 1 illustrates a conventional customer hosted type e-mail system. Fig. 2 shows an Internet email system in accordance with an embodiment of the invention. Fig. 3 shows an exemplary message store in accordance with an embodiment of the invention. Fig. 4 shows a flowchart detailing a process whereby a virtual domain is defined in accordance with an embodiment of the invention. Fig. 5 illustrates a flowchart that details a process that applies a set-of precedence rules to the granting of user-level in accordance with an embodiment of the invention. Fig. 6 illustrates a typical general-purpose computer system suitable for implementing the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to a preferred embodiment of the invention. An example of the preferred embodiment is illustrated in the accompanying drawings. While the invention will be described in conjunction with a preferred embodiment, it will be understood that it is not intended to limit the invention to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. The Internet has effectively lowered the cost of electronic communication. As the number of people and organizations connected to the Internet has grown, the Internet has evolved into a new channel for communication. To facilitate Internet services, Internet messaging clients and easy-to-use web browsers have provided cost-effective way of publishing and sharing information with employees inside the enterprise as well as customers, suppliers, and partners outside. Since messaging services has become crucial to enterprise infrastructure in the 1990s, organizations are seeking messaging solutions that provide a lower cost of ownership while increasing the effectiveness and reliability of their communications network. Specifically, they are evaluating the benefits of Internet standards-based messaging systems. Broadly speaking, the invention describes an Internet standards-based messaging system having a mail server capable of offering e-mail services to multiple organizations each of which has their own virtual domain. The invention is also able to define such virtual domains in the directory and host them on a shared mail server. The invention will now be described in terms of an internet mail server resident on a server computer coupled to a large network of mailboxes typical of a large corporate intranet system as well as a single user coupled to a large interconnected computer network such as the Internet. It should be noted, however, that the inventive mail server is well suited to any application requiring highly reliable, scalable, and efficient information transport over a large number of computers. Referring now to Fig. 2, an Internet email system 300 in accordance with an embodiment of the invention includes an Internet mail server 301 coupled to a user mailbox 303. In the described embodiment, the mail server 301 is a general-purpose, "store-and-forward" system for distributing computer-based mail. It should be noted that the term "store-and-forward" means that the mail server 301 automatically handles the receiving of mail messages necessitated when network links (such as those links 306 to the Internet) or other services are temporarily unavailable. In contrast to mail user agents (MUAs) that are used to create and read electronic mail messages, a transfer unit 302 included in the mail server 301 is responsible for directing messages to the appropriate network transport and ensuring reliable delivery over that transport. In a preferred embodiment, the mail server 301 includes a message store unit 304 coupled to the transfer unit 302 that is used to store messages for later transmission to the user mailbox 303. As shown in Fig. 3, in one implementation, the message store 304 in the mail server 301 is a dedicated data store for the delivery, retrieval, and manipulation of Internet mail messages. In a preferred embodiment, the message store works with the BVIAP4 and POP3 to provide flexible and easy access to messaging. It saves any message that conforms to RFC 822 specifications, and recognizes the Multipurpose Internet Mail Extensions (MIME) content format. In the described embodiment, the message store 304 is organized as a set of folders and user mailboxes. The mailbox 401 is a container for messages where each user has an inbox 402 where new mail arrives, and can have one or more folders 404 where mail can be stored. Folders 404 may contain other folders or mailboxes and may be arranged in a hierarchical tree. Mailboxes owned by an individual user are private folders 406. In addition to a user owning a folder or a mailbox, a common user or group can share the ownership of a folder or mailbox as a shared folder 408. A shared folder is similar to an email group, but instead of messages going into each member of the email group's inbox, messages addressed to the shared folder 408 go into a private folder associated with each user. It should be noted that in a preferred embodiment, the message store 304 maintains only one copy of each message. However, in those cases where the message store 304 receives a message addressed to multiple users or a group (based upon an associated distribution list), it adds a reference to the message in each user's inbox rather than having a copy of the message in each user's inbox, thereby saving disk space. In addition to the reference, the individual message's status (new, unread, replied to, deleted, and the like) is maintained per mailbox. In the described embodiment, access to the message store 304 is multithreaded thereby allowing a single process to manage a large number of connections since each connection is handled by a thread. In this way, multithreaded access maximizes both performance and scalability by minimizing the system resources required for the management of each connection. Referring back to Fig. 2, the delivery and routing of messages by the transfer unit 302 is based on a routing table 310 that in turn is derived from the user and group (distribution list) entries stored in a directory service unit 312. In a preferred embodiment, the directory service unit 312 is the central repository for meta- information: user profiles, distribution lists, and other system resources based upon, in some embodiments, a dedicated Lightweight Directory Access Protocol (LDAP) directory service. This directory supports the storage of information according to a directory information tree (DIT) which is a hierarchical structure that resembles a tree with one major branch at the top and many branches and sub-branches below. The arrangement of the tree is flexible, allowing administrators to decided how to best deploy the service for their organization. For some, it may be best to arrange the tree according the actual business organizational structure or geographic structure. For others, however, a one-to-one mapping to DNS layers may be best. The DIT also provides the flexibility to support a wide range of administration scenarios, and can be administered in either a centralized or distributed manner. Centralized administration can be implemented where one authority manages the entire DIT. This type of administration is usually used in scenarios where the entire DIT resides on one mail server. In order to properly route a message, the transfer unit 302 must access the directory information associated with each message that it processes. However, in a preferred embodiment, rather than querying the directory service 312 directly each time it processes a message, the transfer unit 302 caches the directory information in a directory cache 314. When the transfer unit processes a particular message, it accesses the appropriate directory information in the cache 314. When required, the transfer unit 302 uses the directory information in the cache 314 to update the routing table 312. Since a directory query for each recipient of each message is time-consuming and puts a large load on the mail server 301, by implementing the localized directory cache 314, performance of the email server 301 is improved. In addition, since the information stored in the directory service unit 310 is not always in the format required by the transfer unit 302, when creating the cache, the transfer unit reformats the directory information as required. It should be noted that in most embodiments, a the transfer unit 302 can be configured to adhere to various mail delivery options which specify one or more delivery options for inbound email to a designated recipient. While inbound messages can be delivered into multiple message stores, message access servers (MAS) can read messages from only a designated one of them. The transfer unit 302 uses these to determine the targets of message delivery for all messages submitted to a particular distribution list. Such can include, but are not limited to : "autoreply", "program" where mail is delivered to a program, "forward" where mail is forwarded to another mailbox(es), "file" where the incoming message file is appended to another file, and "shared" where mail is delivered to a shared mailbox (this is typically used to set up a shared mailbox for a distribution list). In the context of electronic mail, protocols are generally a high-level (not necessarily network specific) language spoken between two mailers. Transports are the low-level, network specific details used to implement a protocol on a given network. Thus email messages can come in to the transfer unit 302 by any one of a variety of transports and protocols—submitted directly by a local user, via TCP/IP as an SMTP message from an Internet system, by using a dial-up modem using the PhoneNet protocol, DECnet as a MAIL-11 message, DECnet as an SMTP message, UUCP, an X.400 transport, SNA, and so on. The transfer unit 302 then routes the message out using a transport and protocol appropriate for the message's destination address. In the described embodiment, the transfer unit 302 uses what are referred to as channels to implement specific combinations of transports and protocols. Each different transport and protocol combination has an associated transfer unit channel. The transfer unit 302 postmaster initially configures the transfer unit 302 telling it what sorts of transports and protocols are in use at his site, and what sorts of destination addresses should be routed through which sorts of channels. For instance, at sites with an Internet connection, Internet addresses are normally routed through an SMTP over TCP/IP channel; but at sites with only a UUCP connection, Internet addresses would instead be routed through a UUCP channel. Once the transfer unit 302 is so configured using configuration data stored in a configuration table (not shown), the transfer unit 302 handles message routing and delivery automatically. In this way, ordinary users need never be aware of this underlying transport and routing; that is, they simply address and send their messages and the transfer unit 302 automatically routes and delivers them appropriately. In most embodiments, the transfer unit 302 stores messages as text files. Messages with multiple parts (possibly containing different types of data) are represented as a series of text sections separated by special unique delimiter strings. In the described embodiment, the first few files in each email message are referred to as the message envelope that contains transport information. The message envelope is teπninated by a line containing a boundary marker, or by a line containing two CTRL/A characters. The transfer unit 302 uses the contents of the envelope to make routing decisions. It does not use the content of the message. The content of the envelope is primarily defined by RFC 821. It includes the originator address, the recipient(s) address(es), and envelope ID. The header lines of the message follow the envelope whose format is mandated by RFC 822. It should be noted that there may be any number of message header lines; the message header formed by this collection of header lines is terminated by a single blank line after which follows the message body. An Internet mail message starts with one or more headers. Each header is composed of a field name followed by a colon then a value which can be generated by, for example, the composer of a message or the mail client. A transfer unit can also add headers to a message. Each transfer unit that accepts a message adds a received header to that message. The last transfer unit to accept the message and to actually deliver the message to the message store adds a return-path header. The received and return-path headers provides information that enables you to trace the routing path taken by the message if a problem occurs. Submitted messages from the Internet or local clients go to the transfer unit 302 via SMTP (Simple Mail Transport Protocol). If the message address is within the server 302 domain, the transfer unit 302 delivers the message to the message store 304. If, however, the message is addressed to another domain, the transfer unit 302 relays the message to another transport agent on the Internet or Intranet. In a preferred embodiment, messages to the local domain are stored in the message store 304 depending on how the system is configured. Once messages are delivered to the appropriate mailbox, they can be retrieved, searched for, and manipulated by IMAP4 or POP3-based mail clients. The transfer unit 302 uses the directory 312 that, in a preferred embodiment, is configured as an LDAP type directory, to retrieve local user and group address information. When the transfer unit 302 receives a message, it uses the directory information to determine where the message should be delivered. The message store uses the directory services to authenticate users logging into their mailboxes.. The message store 304 also obtains information about user message quota limits and message store type (IMAP or POP). Outgoing client messages go to the SMTP channel in the LDAP. The transfer unit 302 sends the message to an Internet transfer or, if the address is local, to the message store 304. It should be noted that the LDAP directory 312 is the master repository of all the information related to hosted domains. That is, the message access server retrieves the necessary information to associate a client with a domain from the LDAP directory 312. Similarly, the transfer unit 302 retrieves hosted domain information from the LDAP directory 312 to perform proper routing and address rewriting. Referring now to Fig. 4, showing a flowchart that details a process 500 for defining a virtual domain in accordance with an embodiment of the invention. The process 500 begins at 502 by defining a virtual domain node in the DIT. Once a the virtual domain node has been defined, corresponding routing table entries are defined at 504 and at 506, various virtual domain are stored at the virtual domain node. It should be noted that the various virtual domain include a list of services permitted the domain. Such services include IMAP, IMAPS, POP3, POP3S, SMTP which in some cases requires presentation of credentials. Other of the services include identification of a domain administrator who is authorized to manage the particular virtual domain which includes setting particular user-level for particular users in the domain. These services also include designation of a virtual domain postmaster who identifies email message delivery problems, and a state of the domain. In a preferred embodiment, the state of the domain can be active indicating that all mail can be received, or the state can be inactive, where the particular domain has been temporarily suspended for various and sundry reasons, or, the state of the domain can be deleted indicating that the particular domain no longer exists. Referring now to Fig. 5 that illustrates a flowchart that details a process 600 that applies a set of precedence rules to the granting of user-level in accordance with an embodiment of the invention. The process 600 begins at 602 establishing a set of domain services for the domain. At 604, a set of user level is obtained for a user within the domain. At 606, a determination is made whether or not the set of user level services is a null set. If the set of user level services is not a null set (i.e., certain user lever services have been defined), then a set of allowed services is defined as an intersection of the set of user level services and the set of domain services at 608. If, however, the set of user level services is determined to be a null set (i.e., there are no defined user level services), then the allowed set of user level services is defined as the set of domain services. In either case, control is passed to 612 where it is determined if the requested user level service a member of the set of allowed user level services. If it is determined that the requested service is not a member of the set of allowed user level services, then an error flag is thrown at 614. Otherwise, the requested user level service is confirmed at 616. Fig. 6 illustrates a typical, general-purpose computer system 700 suitable for implementing the present invention. The computer system 700 includes any number of processors 702 (also referred to as central processing units, or CPUs) that are coupled to memory devices including primary storage devices 704 (typically a read only memory, or ROM) and primary storage devices 706 (typically a random access memory, or RAM). Computer system 700 or, more specifically, CPUs 702, may be arranged to support a virtual machine, as will be appreciated by those skilled in the art. One example of a virtual machine that is supported on computer system 700 will be described below with reference to Fig. 8. As is well known in the art, ROM acts to transfer data and instructions uni-directionally to the CPUs 702, while RAM is used typically to transfer data and instructions in a bi-directional manner. CPUs 702 may generally include any number of processors. Both primary storage devices 704, 706 may include any suitable computer-readable media. A secondary storage medium 708, which is typically a mass memory device, is also coupled bi-directionally to CPUs 702 and provides additional data storage capacity. The mass memory device 708 is a computer- readable medium that may be used to store programs including computer code, data, and the like. Typically, mass memory device 708 is a storage medium such as a hard disk or a tape which generally slower than primary storage devices 704, 706. Mass memory storage device 708 may take the form of a magnetic or paper tape reader or some other well-known device. It will be appreciated that the information retained within the mass memory device 708, may, in appropriate cases, be incorporated in standard fashion as part of RAM 706 as virtual rhemory. A specific primary storage device 704 such as a CD-ROM may also pass data uni-directionally to the CPUs 702. CPUs 702 are also coupled to one or more input/output devices 710 that may include, but are not limited to, devices such as video monitors, track balls, mice, keyboards, microphones, touch-sensitive displays, transducer card readers, magnetic or paper tape readers, tablets, styluses, voice or handwriting recognizers, or other well- known input devices such as, of course, other computers. Finally, CPUs 702 optionally may be coupled to a computer or telecommunications network, e.g., an Internet network or an intranet network, using a network connection as shown generally at 712. With such a network connection, it is contemplated that the CPUs 702 might receive information from the network, or might output information to the network in the course of performing the above-described method steps. Such information, which is often represented as a sequence of instructions to be executed using CPUs 702, may be received from and outputted to the network, for example, in the form of a computer data signal embodied in a carrier wave. The above-described devices and materials will be familiar to those of skill in the computer hardware and software arts. Although only a few embodiments of the present invention have been described, it should be understood that the present invention may be embodied in many other specific forms without departing from the spirit or the scope of the present invention. By way of example, operations involved with accessing a user mailbox can be reordered Operations may also be removed or added without departing from the spirit or the scope of the present invention. Although the methods defining a set of precedence rules in a virtual domain in a messaging server in accordance with the present invention are particularly suitable for implementation with respectho a Java™ based environment, the methods may generally be applied in any suitable object-based environment. In particular, the methods are suitable for use in platform-independent object-based environments. It should be appreciated that the methods may also be implemented in some distributed object- oriented systems. While the present invention has been described as being used with a computer system that has an associated virtual machine, it should be appreciated that the present invention may generally be implemented on any suitable object-oriented computer system. Specifically, the methods of defining a virtual domain in accordance with the present invention may generally be implemented in any multi-threaded, object-oriented system without departing from the spirit or the scope of the present invention. Therefore, the present examples are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope of the appended claims along with their full scope of equivalents. What is claimed is:

Claims: In the claims; 1. A method of granting a user level service to a user residing in a domain having an associated set of allowed domain level services, comprising: (a) receiving a request for the user level service; (b) determining if the requested user level service is a member of a proper subset of the set of allowed domain level services; and (c) granting the requested user level service if the requested user level service is a member of the proper subset of the set of allowed domain level services such that the granted user level service is an allowed user level service. 2. A method as recited in claim 1, wherein when the requested user level service is determined to not be a member of the proper subset of allowed domain level services, then the requested user level service is not granted and is a non-allowed user level service. 3. A method as recited in claim 2, wherein when the user requests a plurality of user level services, then only those of the requested plurality of services that are members of the proper subset of allowed domain level services are granted such that the granted user level services are members of the set of allowed user level services. 4. A method as recited in claim 3, wherein when the set of domain level services is reduced, then, (d) comparing the reduced set of domain level services to the set of allowed user level services. 5. A method as recited in claim 4, wherein the set of allowed user level services is reduced based upon the comparing (d). 6. A method as recited in claim 3, wherein when the set of domain level services is expanded, then, (e) comparing the expanded set of domain level services to the set of allowed user level services. 7. A method as recited in claim 6, wherein the set of allowed user level services is expanded based upon the comparing (e). 8. A method as recited in claim 4, wherein the allowed service is selected from the group comprising: IMAP, MAPS, POP3, POP3S, and SMTP. 9. A method as recited in claim 8,wherein the allowed service is a security service requiring a credential. 10. A computer-readable medium containing programming instructions for granting a user level service to a user residing in a domain having an associated set of allowed domain level services, the computer-readable medium comprising computer program code devices configured to cause a computer to execute the operations of: (a) receiving.a request for the user level service; (b) determining if the requested user level service is a member of a proper subset of the set of allowed domain level services; and (c) granting the requested user level service if the requested user level service is a member of the proper subset of the set of allowed domain level services such that the granted user level service is an allowed user level service. 11. A computer-readable medium containing programming instructions for granting a user level service to a user residing in a domain having an associated set of allowed domain level services as recited in claim 10, the computer-readable medium further comprising computer program code devices configured to cause a computer to execute the operations of: wherein when the requested user level service is determined to not be a member of the proper subset of allowed domain level services, then the requested user level service is not granted and is a non-allowed user level service. 12. A computer-readable medium containing programming instructions for granting a user level service to a user residing in a domain having an associated set of allowed domain level services as recited in claim 10, the computer-readable medium further comprising computer program code devices configured to cause a computer to execute the operations of: when the user requests a plurality of user level services, then only those of the requested plurality of services that are members of the proper subset of allowed domain level services are granted such that the granted user level services are members of the set of allowed user level services.

Inventors: HUFF DARYL A, MISNER TIMOTHY C, SRIVASTAVA ANIL K, HUFF, DARYL, A., MISNER, TIMOTHY, C., SRIVASTAVA, ANIL, K.
Applicants: SUN MICROSYSTEMS INC, SUN MICROSYSTEMS, INC.
Application year: 2001
Main classification: G06F15
IPC codes: G06F1, H04L12, H04L29