It’s always important to understand the history of something in order to understand why it’s important! Learn about how Email Marketing evolved as well as the challenges of offline direct-to-consumer or direct business-to-business marketing communications that Email Marketing has provided a solution to.

 

Remember the Days of Postal Mail Marketing?

Take a minute and take a walk to your mailbox. No, we don’t mean walk to your computer to check your inbox. We mean a walk to your actual, physical mailbox where people mail you paper letters and packages. Now take a moment to sort through the mail that you find there. Chances are that you will find several promotional or marketing flyers which are trying to sell you localized services. However, you may also find catalogs and promotional postcards for global or larger brands.

Now, take a moment to consider what the world would be like if postal mail to your physical mailbox were the only way to send you customized communications to market products and services. It would be a highly inefficient system. Because postal mailings need to be printed in bulk to reduce costs, your message could only be mildly customized to include your name. Then, whoever wanted to advertise to you would have to pay for not only the printing of the postcard, flyer or catalog to be mailed, but also for all of the stamps or postal costs to send the mailing. Finally, the marketer who sent the mailing would have to wait for a period of time for you to receive it. It may be several weeks until the post office delivered it, and it may be even longer until you removed the mailing from your mailbox and read it. Because of that timing, the offer that the marketer was sending to you couldn’t be specific and time relevant. Finally, the marketer had no way of knowing if the postal mailing had had any impact on you unless you then used a specific promotional code included on the mailing. There was no way to know if you’d even looked at or received your mailing!

Does this sound like an ineffective way to market your products or services to a mass consumer audience? Well, until as recently as the 1990s, it was largely the only way to get a marketing communication into the hands of a specific individual. Marketers came up with many ways to attempt to make postal marketing mailings more personalized and to better track their response rates, but the truth was that once you sent a postal mailing, figuring out if it worked or didn’t work was more guess-work than actual facts. The entire process was, and is, expensive, time consuming and difficult to judge the success of.

Fortunately for you and your consumer or business-to-business marketing needs, the 1990’s happened and the internet was born. Soon after, email began to become a primary form of both personal and business communications. Not long after the popularity of personal email exploded, email marketing became a specialty area for those with marketing expertise because of its improved capacity for customization, segmentation, frequency, relevancy of communications and, most importantly, tracking capabilities.

1991: The “Birth” of the Internet

While there are many people who “claim” to be the founder of the internet, experts say that the internet as we know it began in 1991 when CERN (the European Organization for Nuclear Research) publicized a paper known as the New World Wide Web Project. Though a British scientist, Tim Berners-Lee, had actually been creating html, http and the world’s very first web pages at CERN as early as two years prior to the paper, the publishing of the paper is considered the “birth” of the internet. Not only did the internet change life as we know it, it also changed marketing as we know it!

Over the next decade, many experts estimate that the internet grew as much as one hundred percent per year in terms of bandwidth used. The greatest spikes of growth were seen in 1996 and 1997. Today, of course, you would have a hard time finding anybody who does not admit that the internet plays a key role in their daily lives, from information gathering to processing communications, primarily through the use of email and, more recently, social media.

1996: Hotmail Becomes the First Web-Based Email Service

One of the greatest benefits of the rise of the internet was the ability to use email, or electronic mail, to communicate with people. Email was fast, free and could speed up communications across the world in a way that most people had not previously imagined. However, during the first years of the internet, email was only available to people who fit into specific groups: college students using their college email address or employees who were able to use corporate email addresses. The second group typically had significant limitations on how they could use their email and whom they could communicate with. While some individuals could also get email services provided by their Internet Service Provider (ISP), those services typically required that you checked your email specifically from the computer that was supported by your ISP. Email was not a “pick up and go anywhere” type of communication.

Then, in 1996, Sabeer Bhatia and Jack Smith launched what was then called HoTMaiL (with the letters being a reference to html). It was the first web-based email system, and suddenly email was available to anybody who had access to the internet. That didn’t just mean people who had home computers that were internet wired. It also meant anybody who could use a public computer at a library or business center. Suddenly, email was no longer limited to just a small group of people who needed to communicate primarily with each other. Email was out of the bag to the public, and anybody who wanted to communicate with anybody else could do so via HoTMaiL. Not surprisingly, people loved the service and flocked to it. A year later in 1997, Microsoft purchased HoTMaiL for four hundred million dollars and renamed it MSN Hotmail.

Just How Many People Use Email Today?

Today, Hotmail is still technically the largest web-based email service in terms of raw users, according to the most recent comScore data (August of 2010). Hotmail is reported to have three hundred and sixty-four million users. Yahoo! mail is the second largest with a reported two hundred and eighty million users, and Google’s Gmail is third with one hundred and ninety-one million users.

The Birth of Email Marketing

While email began as a communications tool for academic and business purposes, it soon became a tool for personal communications among friends, relatives and even people who had never met in real life! As people began to spend more and more time using email as their primary communications tool, smart marketers realized that email communications were the future of marketing communications and began to make the shift into using email as a way to effectively communicate with customers. Email marketing, even in its earliest days, presented a number of benefits over both postal marketing and telesales as a form of direct-to-consumer or direct business-to-business communications. We’ll look at those benefits in detail in the next section of this book, but today email marketing is a robust portion of any complete marketing plan and has entire industries built around helping businesses of all sizes effectively email market.

SMTPSERVER.in would, of course, be an example of this. SMTPSERVER.in works to develop email products that streamline the sending of email to consumers or business contacts with customized messages and complete tracking. In addition to companies that focus primarily on developing email marketing solutions, individuals have become email marketing experts as well. Most mid-sized or larger companies employ at least one email marketing specialist and may have as many as several employees who focus on nothing but creating effective email marketing strategies and campaigns.

Of course, you may not need an entire staff, but you do need to understand the basics of email marketing strategy, benefits and tactics of email marketing. We’ll cover all of those in this book to make you your own email marketing expert by the end!

Hi yesterday i was trying to install Photoshop CS3 on a system having Windows Server 2003 installed.

But it gives me an error saying that you need a OS equivalent to Windows XP SP2 or greater or Windows Vista.

So i found a workaroud which i would like to share with you.

Just download a utility from Microsoft called Application Verifier its a small but very benificial utility.Link is http://www.microsoft.com/downloads/details.aspx?FamilyID=C4A25AB9-649D-4A1B-B4A7-C9D8B095DF18&displaylang=en

1.Run the Application Verifier and open the setup.exe file for photoshop cs3 and go to the compatibility tree view column.

2.Go to HighVersionLie and right click it to get properties.

3.Now suppose if you want to any program assume that you are using Windows XP SP2 then enter like below figure in the boxes that follow

4.Click OK And then Save

5.It will then ask you for the debugger to be attached do not attach any debugger and click save .

6.Now if you try installing it will be installed with no problems.

Simple Mail Transfer Protocol

An SMTP server is a computer that receives outgoing mail messages from users and routes them to their intended recipients. All SMTP servers implement some version of the Simple Mail Transport Protocol, and many that run Unix use the sendmail program. Messages often must pass through several servers to reach their destinations, and SMTP facilitates this.

Simple Mail Transfer Protocol (SMTP) is an Internet standard for electronic mail (e-mail) transmission across Internet Protocol (IP) networks. SMTP was first defined in RFC 821 (STD 15) (1982),[1] and last updated by RFC 5321 (2008)[2] which includes the extended SMTP (ESMTP) additions, and is the protocol in widespread use today. SMTP is specified for outgoing mail transport and uses TCP port 25. The protocol for new submissions is effectively the same as SMTP, but it uses port 587 instead.

While electronic mail servers and other mail transfer agents use SMTP to send and receive mail messages, user-level client mail applications typically only use SMTP for sending messages to a mail server for relaying. For receiving messages, client applications usually use either the Post Office Protocol (POP) or the Internet Message Access Protocol (IMAP) or a proprietary system (such as Microsoft Exchange or Lotus Notes/Domino) to access their mail box accounts on a mail server.

* 1 History
* 2 Mail processing model
* 3 Protocol overview
o 3.1 SMTP vs mail retrieval
o 3.2 Remote Message Queue Starting
o 3.3 On-Demand Mail Relay
o 3.4 Internationalization
* 4 Outgoing mail SMTP server
* 5 SMTP transport example
* 6 Optional extensions
* 7 Security and spamming
* 8 Implementations
* 9 Related Requests For Comments
* 10 See also


History

Various forms of one-to-one electronic messaging were used in the 1960s. People communicated with one another using systems developed for specific mainframe computers. As more computers were interconnected, especially in the US Government's ARPANET, standards were developed to allow users using different systems to be able to e-mail one another. SMTP grew out of these standards developed during the 1970s.

SMTP can trace its roots to two implementations described in 1971, the Mail Box Protocol, which has been disputed to actually have been implemented,[3] but is discussed in RFC 196 and other RFCs, and the SNDMSG program, which, according to RFC 2235, Ray Tomlinson of BBN "invents" for TENEX computers the sending of mail across the ARPANET.[4][5][6] Fewer than 50 hosts were connected to the ARPANET at this time.[7]

Further implementations include FTP Mail [8] and Mail Protocol, both from 1973.[9] Development work continued throughout the 1970s, until the ARPANET converted into the modern Internet around 1980. Jon Postel then proposed a Mail Transfer Protocol in 1980 that began to remove the mail's reliance on FTP.[10] SMTP was published as RFC 821 in August 1982, also by Postel.

The SMTP standard was developed around the same time as Usenet, a one-to-many communication network with some similarities.

SMTP became widely used in the early 1980s. At the time, it was a complement to Unix to Unix Copy Program (UUCP) mail, which was better suited to handle e-mail transfers between machines that were intermittently connected. SMTP, on the other hand, works best when both the sending and receiving machines are connected to the network all the time. Both use a store and forward mechanism and are examples of push technology. Though Usenet's newsgroups are still propagated with UUCP between servers,[11] UUCP mail has virtually disappeared[12] along with the "bang paths" it used as message routing headers.

The article about sender rewriting contains technical background info about the early SMTP history and source routing before RFC 1123.

Sendmail was one of the first (if not the first) mail transfer agents to implement SMTP.[citation needed] Some other popular SMTP server programs include Postfix, qmail, Novell GroupWise, Exim, Novell NetMail, Microsoft Exchange Server, Sun Java System Messaging Server.

Message submission (RFC 2476) and SMTP-AUTH (RFC 2554) were introduced in 1998 and 1999, both describing new trends in e-mail delivery. Originally, SMTP servers were typically internal to an organization, receiving mail for the organization from the outside, and relaying messages from the organization to the outside. But as time went on, SMTP servers (Mail transfer agents), in practice, were expanding their roles to become message submission agents for Mail user agents, some of which were now relaying mail from the outside of an organization. (e.g. a company executive wishes to send e-mail while on a trip using the corporate SMTP server.) This issue, a consequence of the rapid expansion and popularity of the World Wide Web, meant that the SMTP protocol had to include specific rules and methods for relaying mail and authenticating users to prevent abuses such as relaying of unsolicited e-mail (spam).

As this protocol started out purely ASCII text-based, it did not deal well with binary files. Standards such as Multipurpose Internet Mail Extensions (MIME) were developed to encode binary files for transfer through SMTP. Mail transfer agents (MTAs) developed after Sendmail also tended to be implemented 8-bit-clean, so that the alternate "just send eight" strategy could be used to transmit arbitrary text data (in any 8-bit ASCII-like character encoding) via SMTP. 8-bit-clean MTAs today tend to support the 8BITMIME extension, permitting binary files to be transmitted almost as easily as plain text.

Many people contributed to the core SMTP specifications, among them Jon Postel, Eric Allman, Dave Crocker, Ned Freed, Randall Gellens, John Klensin, and Keith Moore.
Mail processing model
Blue arrows can be implemented using SMTP variations.

The overall flow for message creation, mail transport, and delivery may be illustrated as shown.

Email is submitted by a mail client (MUA, mail user agent) to a mail server (MSA, mail submission agent) using SMTP on TCP port 587. Most mailbox providers still allow submission on traditional port 25. From there, the MSA delivers the mail to its MTA. Often, these two agents are just different instances of the same software launched with different options on the same machine. Local processing can be done either on a single machine, or split among various appliances; in the former case, involved processes can share files; in the latter case, SMTP is used to transfer the message internally, with each host configured to use the next appliance as a smart host. Each process is an MTA in its own right; that is, an SMTP server.

The boundary MTA has to locate the target host. It uses the in the Domain name system (DNS) to look up the the mail exchanger record (MX record) for the recipient's domain (the part of the address on the right of @). The returned MX record contains the name of the target host. The MTA next looks up the A record for that name in order to get the IP address and connect to such host as an SMTP client. (The article on MX record discusses many factors in determining which server the sending MTA connects to.)

Once the MX target accepts the incoming message, it hands it to a mail delivery agent (MDA) for local mail delivery. An MDA is able to save messages in the relevant mailbox format. Again, mail reception can be done using many computers or just one —the picture displays two nearby boxes in either case. An MDA may deliver messages directly to storage, or forward them over a network using SMTP, or any other means, including the Local Mail Transfer Protocol (LMTP), a derivative of SMTP designed for this purpose.

Once delivered to the local mail server, the mail is stored for batch retrieval by authenticated mail clients (MUAs). Mail is retrieved by end-user applications, called email clients, using Internet Message Access Protocol (IMAP), a protocol that both facilitates access to mail and manages stored mail, or the Post Office Protocol (POP) which typically uses the traditional mbox mail file format or a proprietary system such as Microsoft Exchange/Outlook or Lotus Notes/Domino. Webmail clients may use either method, but the retrieval protocol is often not a formal standard.

SMTP defines message transport, not the message content. Thus, it defines the mail envelope and its parameters, such as the envelope sender, but not the header or the body of the message itself. STD 10 and RFC 5321 define SMTP (the envelope), while STD 11 and RFC 5322 define the message (header and body), formally referred to as the Internet Message Format.
Protocol overview

SMTP is a text-based protocol, in which a mail sender communicates with a mail receiver by issuing command strings and supplying necessary data over a reliable ordered data stream channel, typically a Transmission Control Protocol (TCP) connection. An SMTP session consists of commands originated by an SMTP client (the initiating agent, sender, or transmitter) and corresponding responses from the SMTP server (the listening agent, or receiver) so that the session is opened, and session parameters are exchanged. A session may include zero or more SMTP transactions. An SMTP transaction consists of three command/reply sequences (see example below.) They are:

1. MAIL command, to establish the return address, a.k.a. Return-Path, 5321.From, mfrom, or envelope sender. This is the address for bounce messages.
2. RCPT command, to establish a recipient of this message. This command can be issued multiple times, one for each recipient. These addresses are also part of the envelope.
3. DATA to send the message text. This is the content of the message, as opposed to its envelope. It consists of a message header and a message body separated by an empty line. DATA is actually a group of commands, and the server replies twice: once to the DATA command proper, to acknowledge that it is ready to receive the text, and the second time after the end-of-data sequence, to either accept or reject the entire message.

Besides the intermediate reply for DATA, each server's reply can be either positive (2xx reply codes) or negative. Negative replies can be permanent (5xx codes) or transient (4xx codes). A reject is a permanent failure by an SMTP server; in this case the SMTP client should send a bounce message. A drop is a positive response followed by message discard rather than delivery.

The initiating host, the SMTP client, can be either an end-user's email client, functionally identified as a mail user agent (MUA), or a relay server's mail transfer agent (MTA), that is an SMTP server acting as an SMTP client, in the relevant session, in order to relay mail. Fully-capable SMTP servers maintain queues of messages for retrying message transmissions that resulted in transient failures.

A MUA knows the outgoing mail SMTP server from its configuration. An SMTP server acting as client, i.e. relaying, typically determines which SMTP server to connect to by looking up the MX (Mail eXchange) DNS resource record for each recipient's domain name. Conformant MTAs (not all) fall back to a simple A record in case no MX record can be found. Relaying servers can also be configured to use a smart host.

An SMTP server acting as client initiates a TCP connection to the server on the "well-known port" designated for SMTP: port 25. MUAs should use port 587 to connect to an MSA. The main difference between an MTA and an MSA is that SMTP Authentication is mandatory for the latter only.
SMTP vs mail retrieval

SMTP is a delivery protocol only. It cannot pull messages from a remote server on demand. Other protocols, such as the Post Office Protocol (POP) and the Internet Message Access Protocol (IMAP) are specifically designed for retrieving messages and managing mail boxes. However, the SMTP protocol has a feature to initiate mail queue processing on a remote server so that the requesting system may receive any messages destined for it (cf. Remote Message Queue Starting). POP and IMAP are preferred protocols when a user's personal computer is only intermittently powered up, or Internet connectivity is only transient and hosts cannot receive message during off-line periods.
Remote Message Queue Starting

Remote Message Queue Starting is a feature of the SMTP protocol that permits a remote host to start processing of the mail queue on a server so it may receive messages destined to it by sending the TURN command. This feature however was deemed insecure[13] and was extended in RFC 1985 with the ETRN command which operates more securely using an authentication method based on Domain Name System information.
On-Demand Mail Relay
Main article: On-Demand Mail Relay
Internationalization

RFC 5336 describes internationalization features for SMTP, the UTF8SMTP extension, which provides support for multi-byte and non-ASCII characters in email addresses, such as Pelé@live.com (simple diacritic), δοκιμή@παράδειγμα.δοκιμή, and 测试@测试.测试.

Outgoing mail SMTP server

An e-mail client requires the name or the IP address of an SMTP server as part of its configuration. The server will deliver messages on behalf of the user. This setting allows for various policies and network designs. End users connected to the Internet can use the services of an e-mail provider that is not necessarily the same as their connection provider (ISP). Network topology, or the location of a client within a network or outside of a network, is no longer a limiting factor for e-mail submission or delivery. Modern SMTP servers typically use a client's credentials (authentication) rather than a client's location (IP address), to determine whether it is eligible to relay e-mail.

Server administrators choose whether clients use TCP port 25 (SMTP) or port 587 (Submission), as formalized in RFC 4409, for relaying outbound mail to a mail server. The specifications and many servers support both. Although some servers support port 465 for legacy secure SMTP in violation of the specifications, it is preferable to use standard ports and standard ESMTP commands[14] according to RFC 3207 if a secure session needs to be used between the client and the server. Some servers are set up to reject all relaying on port 25, but valid users authenticating on port 587 are allowed to relay mail to any valid address. A server that relays all e-mail for all destinations for all clients connecting to port 25 is known as an open relay and is now generally considered a bad practice worthy of blacklisting.

Some Internet service providers intercept port 25, so that it is not possible for their users to send mail via a relaying SMTP server outside the ISP's network using port 25; they are restricted to using the ISP's SMTP server. Some independent SMTP servers support an additional port other than 25 to allow users with authenticated access to connect to them even if port 25 is blocked. The practical purpose of this is that a mobile user connecting to different ISPs otherwise has to change SMTP server settings on the mail client for each ISP; using a relaying SMTP server allows the SMTP client settings to be used unchanged worldwide.

SMTP transport example

A typical example of sending a message via SMTP to two mailboxes (alice and theboss) located in the same mail domain (example.com) is reproduced in the following session exchange.

For illustration purposes here (not part of protocol), the protocol exchanges are prefixed for the server (S:) and the client (C:).

After the message sender (SMTP client) establishes a reliable communications channel to the message receiver (SMTP server), the session is opened with a greeting by the server, usually containing its fully qualified domain name (FQDN), in this case smtp.example.com. The client initiates its dialog by responding with a HELO command identifying itself in the command's parameter with its FQDN (or an address literal if none is available).[2]

S: 220 smtp.smtpserver.com ESMTP Postfix
C: HELO relay.examplesmtpserver.org
S: 250 Hello relay.example.org, I am glad to meet you
C: MAIL FROM:<bob@examplesmtpserver.org>
S: 250 Ok
C: RCPT TO:<alice@examplesmtpserver.com>
S: 250 Ok
C: RCPT TO:<theboss@examplesmtpserver.com>
S: 250 Ok
C: DATA
S: 354 End data with <CR><LF>.<CR><LF>
C: From: "Bob Example" <bob@examplesmtpserver.org>
C: To: "Alice Example" <alice@examplesmtpserver.com>
C: Cc: theboss@examplesmtpserver.com
C: Date: Tue, 15 Jan 2008 16:02:43 -0500
C: Subject: Test message
C:
C: Hello Alice.
C: This is a test message with 5 header fields and 4 lines in the message body.
C: Your friend,
C: Bob
C: .
S: 250 Ok: queued as 12345
C: QUIT
S: 221 Bye
{The server closes the connection}

The client notifies the receiver of the originating email address of the message in a MAIL FROM command. In this example, the email message is sent to two mailboxes on the same SMTP server: one each for each recipient listed in the To and Cc header fields. The corresponding SMTP command is RCPT TO. Each successful reception and execution of a command is acknowledged by the server with a result code and response message (e.g., 250 Ok).

The transmission of the body of the mail message is initiated with a DATA command after which it is transmitted verbatim line by line and is terminated with an end-of-data sequence. This consists of a new-line (<CR><LF>), a single full stop (period), followed by another new-line. Since a message body can contain a line with just a period as part of the text, the client sends two periods every time a line starts with a period; correspondingly, the server replaces every sequence of two periods at the beginning of a line with a single one. Such escaping method is called dot-stuffing.

The server's positive reply to the end-of-data, as exemplified, implies that the server has taken the responsibility of delivering the message. A message can be doubled if there is a communication failure at this time, e.g. due to a power shortage: Until the sender has not received that 250 reply, it must assume the message was not delivered. On the other hand, after the receiver has decided to accept the message, it must assume the message has been delivered to it. Thus, during this time span, both agents have active copies of the message that they will try to deliver[15]. The probability that a communication failure occurs exactly at this step is directly proportional to the amount of filtering that the server performs on the message body, most often for anti-spam purposes. The limiting timeout is specified to be 10 minutes.[16]

The QUIT command ends the session. If the second recipient were located elsewhere, the client would QUIT and connect to the appropriate SMTP server after the first message had been queued. The information that the client sends in the HELO and MAIL FROM commands are added (not seen in example code) as additional header fields to the message by the receiving server. It adds a Received and Return-Path header field, respectively.
Optional extensions

Although optional and not shown in this example, many clients ask the server for the SMTP extensions that the server supports, by using the EHLO greeting of the extended SMTP specification (RFC 1870). Clients fall back to HELO only if the server does not respond to EHLO.

Modern clients may use the ESMTP extension keyword SIZE to query the server for the maximum message size that will be accepted. Older clients and servers may try to transfer excessively-sized messages that will be rejected after consuming network resources, including connect time to network links that is paid by the minute.

Users can manually determine in advance the maximum size accepted by ESMTP servers. The client replaces the HELO command with the EHLO command.

S: 220 smtp2.examplesmtpserver.com ESMTP Postfix
C: EHLO bob.examplesmtpserver.org
S: 250-smtp2.example.com Hello bob.examplesmtpserver.org [192.0.2.201]
S: 250-SIZE 14680064
S: 250-PIPELINING
S: 250 HELP

Thus smtp2.examplesmtpserver.com declares that it will accept a fixed maximum message size no larger than 14,680,064 octets (8-bit bytes). Depending on the server's actual resource usage, it may be currently unable to accept a message this large. In the simplest case, an ESMTP server will declare a maximum SIZE with only the EHLO user interaction.
Security and spamming
Main article: Anti-spam techniques (e-mail)

The original SMTP specification did not include a facility for authentication of senders. Subsequently, the SMTP-AUTH extension was defined by RFC 2554.[17] The SMTP extension (ESMTP) provides a mechanism for email clients to specify a security mechanism to a mail server, authenticate the exchange, and negotiate a security profile (Simple Authentication and Security Layer, SASL) for subsequent message transfers.

Microsoft products implement the proprietary Secure Password Authentication (SPA) protocol through the use of the SMTP-AUTH extension.

However, the impracticality of widespread SMTP-AUTH implementation and management means that E-mail spamming is not and cannot be addressed by it.

Modifying SMTP extensively, or replacing it completely, is not believed to be practical, due to the network effects of the huge installed base of SMTP. Internet Mail 2000 was one such proposal for replacement.

Spam is enabled by several factors, including vendors implementing broken MTAs (that do not adhere to standards, and therefore make it difficult for other MTAs to enforce standards), security vulnerabilities within the operating system (often exacerbated by always-on broadband connections) that allow spammers to remotely control end-user PCs and cause them to send spam, and a lack of "intelligence" in many MTAs.

There are a number of proposals for sideband protocols that will assist SMTP operation. The Anti-Spam Research Group (ASRG) of the Internet Research Task Force (IRTF) is working on a number of E-mail authentication and other proposals for providing simple source authentication that is flexible, lightweight, and scalable. Recent Internet Engineering Task Force (IETF) activities include MARID (2004) leading to two approved IETF experiments in 2005, and DomainKeys Identified Mail in 2006.
Implementations
Main article: List of mail servers
Related Requests For Comments

* RFC 1123 – Requirements for Internet Hosts—Application and Support (STD 3)
* RFC 1870 – SMTP Service Extension for Message Size Declaration (оbsoletes: RFC 1653)
* RFC 2505 – Anti-Spam Recommendations for SMTP MTAs (BCP 30)
* RFC 2920 – SMTP Service Extension for Command Pipelining (STD 60)
* RFC 3030 – SMTP Service Extensions for Transmission of Large and Binary MIME Messages
* RFC 3207 – SMTP Service Extension for Secure SMTP over Transport Layer Security (obsoletes RFC 2487)
* RFC 3461 – SMTP Service Extension for Delivery Status Notifications (obsoletes RFC 1891)
* RFC 3462 – The Multipart/Report Content Type for the Reporting of Mail System Administrative Messages (obsoletes RFC 1892)
* RFC 3463 – Enhanced Status Codes for SMTP (obsoletes RFC 1893 )
* RFC 3464 – An Extensible Message Format for Delivery Status Notifications (obsoletes RFC 1894)
* RFC 3834 – Recommendations for Automatic Responses to Electronic Mail
* RFC 4409 – Message Submission for Mail (obsoletes RFC 2476)
* RFC 4952 – Overview and Framework for Internationalized E-mail
* RFC 4954 – SMTP Service Extension for Authentication (obsoletes RFC 2554)
* RFC 5068 – E-mail Submission Operations: Access and Accountability Requirements (BCP 134)
* RFC 5321 – The Simple Mail Transfer Protocol (obsoletes RFC 821 aka STD 10, RFC 974, RFC 1869, RFC 2821)
* RFC 5322 – Internet Message Format (obsoletes RFC 822 aka STD 11, and RFC 2822)
* RFC 5336 - SMTP Extension for Internationalized Email Addresses (updates RFC 2821, RFC 2822, and RFC 4952)
* RFC 5504 - Downgrading Mechanism for Email Address Internationalization

See also

* Bounce messages (SMTP non-delivery reports), bounce address
* Comparison of mail servers
* E-mail authentication
* E-mail encryption
* Extended SMTP (ESMTP)
* Ident
* List of mail servers
* POP before SMTP / SMTP after POP
* Sender Policy Framework (SPF)
* SMTP-AUTH (ESMTPA)
* Variable envelope return path

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com ; Global ;whois.internic.net;No match for

com ; Global ;whois.centralnic.com;No match

com ; Global ;whoisfinder.com;No match

com ; Global ;ripe.net;No match

com ; Global ;truewhois.com;No match

coop ; Global ;whois.nic.coop;

cx ; Christmas Island ;whois.nic.cx;No match for

cz ; Czech Republic ;whois.nic.cz;No data found

de ; Germany ;whois.denic.de;

de ; Germany ;whois.nic.de;No entries found

dk ; Denmark ;whois.dk-hostmaster.dk;No entries found

ec ; Ecuador ;whois.lac.net;No match found

edu ; United States ;whois.verisign-grs.net;

edu ; United States ;whois.internic.net;No match

edu ; United States ;whois.networksolutions.com;There is no match

ee ; Estonia ;whois.eenet.ee;

eg ; Egypt ;whois.ripe.net;No entries found

es ; Spain ;whois.ripe.net;No entries found

fi ; Finland ;whois.ripe.net;No entries found

fo ; Faroe Islands ;whois.ripe.net;No entries found

fr ; France ;whois.nic.fr;No entries found

ge ; Georgia ;whois.ripe.net;No entries found

gf ; French Guiana ;whois.nplus.gf;not found in our database

gg ; Channel Islands

gl ; Greenland ;whois.ripe.net;No entries found

gov ; United States ;whois.nic.gov;No match for

gr ; Greece ;whois.ripe.net;No entries found

gs ; South Georgia & South Sandwich Islands ;whois.adamsnames.tc;is not registered

hk ; Hong Kong ;whois.hkdnr.net.hk;No Match for

hm ; Heard & McDonald Islands ;whois.registry.hm;

hr ; Croatia (Hrvatska) ;whois.ripe.net;No entries found

hu ; Hungary ;whois.nic.hu;

id ; Indonesia ;muara.idnic.net.id;

ie ; Eire (Ireland) ;whois.domainregistry.ie;% There was no match in the IE Domain

il ; Israel ;whois.isoc.org.il;No data was found

in ; India ;whois.iisc.ernet.in;no entries found

info ; Global ;whois.afilias.info;NOT FOUND

int ; Global ;whois.iana.org;

is ; Iceland ;whois.isnic.is;No entries found

it ; Italy ;whois.nic.it;No entries found

je ; Channel Islands

jo ; Jordan ;whois.ripe.net;No entries found

jp ; Japan ;whois.nic.ad.jp;No match

kg ; Kyrgyzstan ;whois.domain.kg;

kr ; Republic of South Korea ;whois.krnic.net;

kr ; Republic of South Korea ;whois.nic.or.kr;is not registered

kz ; Kazakhstan ;whois.domain.kz;No entries found

la ; Lao People's Democratic Republic ;whois.nic.la;

li ; Liechtenstein ;whois.nic.ch;

li ; Liechtenstein ;whois.nic.li;No match for

lk ; Sri Lanka ;whois.nic.lk;

lt ; Lithuania ;ns.litnet.lt;

lu ; Luxembourg ;whois.dns.lu;No entries found

lv ; Latvia ;whois.ripe.net;No entries found

eu.lv; Latvia ;whois.biz;Not found

ma ; Morocco ;whois.ripe.net;No entries found

mc ; Monaco ;whois.ripe.net;No entries found

md ; Moldova ;whois.ripe.net;No entries found

mil ; United States ;whois.nic.mil;

mil ; United States ;whois.internic.net;No match for

mil ; United States ;whois.networksolutions.com;There is no match

mk ; Macedonia

mm ; Burma (Myanmar) ;whois.nic.mm;No domains matched

ms ; Montserrat ;whois.adamsnames.tc;is not registered

mt ; Malta ;whois.ripe.net;No entries found

museum ; Global ;whois.mdma.museum;

mx ; Mexico ;whois.nic.mx;Referencias de Organization No Encontradas

name ; Global ;whois.nic.name;No match

net ; Global ;whois.verisign-grs.net;

net ; Global ;whois.crsnic.net;No match for

net ; Global ;whois.networksolutions.com;There is no match

net ; Global ;whois.internic.net;No match for

net ; Global ;whois.centralnic.com;No match

nl ; Netherlands ;whois.domain-registry.nl;not a registered domain

no ; Norway ;whois.norid.no;no matches

nu ; Niue ;whois.worldnames.net;

nu ; Niue ;whois.nic.nu;NO MATCH for

nz ; New Zealand ;akl-iis.domainz.net.nz;

org ; Global ;whois.publicinterestregistry.net;NOT FOUND

pl ; Poland ;nazgul.nask.waw.pl;

pl ; Poland ;whois.dns.pl;does not exists

pro ; Global ;whois.internic.net;No match for

pt ; Portugal ;whois.ripe.net;No entries found

ro ; Romania ;whois.rotld.ro;No entries found

ru ; Russian Federation ;whois.ripn.ru;No entries found

ru ; Russian Federation ;whois.ripn.net;No entries found

rw ; Rwanda ;whois.cd;

se ; Sweden ;ear.nic-se.se;No data found

sg ; Singapore ;qs.nic.net.sg;

sg ; Singapore ;whois.nic.net.sg;NOMATCH

sh ; St. Helena ;whois.nic.sh;No match

si ; Slovenia ;whois.arnes.si;No entries found

sk ; Slovakia ;whois.ripe.net;No entries found

sm ; San Marino ;whois.ripe.net;No entries found

st ; Principe & Sao Tome ;whois.nic.st;No entries found

tc ; Turks & Caicos Islands ;whois.adamsnames.tc;is not registered

tf ; French Southern Territories ;whois.adamsnames.tc;is not registered

th ; Thailand ;whois.thnic.net;No entries

tj ; Tajikistan ;whois.nic.tj;No match

tk ; Tokelau ;whois.dot.tk;not known

tm ; Turkmenistan ;whois.nic.tm;No match

tn ; Tunisia ;whois.ripe.net;No entries found

to ; Tonga ;whois.tonic.to;No match for

tr ; Turkey ;whois.ripe.net;No entries found

tr ; Turkey ;whois.metu.edu.tr;Not found in database

tv ; Tuvalu ;whois.tv;

tv ; Tuvalu ;whois.internic.net;No match for

tw ; Taiwan ;whois.twnic.net;No Records Found

ua ; Ukraine ;whois.net.ua;% No entries found

uk ; United Kingdom ;whois.nic.uk;No match

uk ; United Kingdom ;whois.ja.net;No such domain

us ; United States ;whois.nic.us;Not found:

fed.us; United States ;whois.nic.mil;

va ; Vatican City State (Holy See) ;whois.ripe.net;No entries found

vg ; British Virgin Islands ;whois.adamsnames.tc;is not registered

ws ; Samoa ;whois.worldsite.ws;

ws ; Samoa ;whois.nic.ws;No match for

ws ; Samoa ;whois.godaddy.com; No match for

yu ; Yugoslavia ;whois.ripe.net;No entries found

za ; South Africa ;apies.frd.ac.za;

za ; South Africa ;whois.co.za;No information available

Making synchronous calls to web services can be problematic on occasion, because they have the potential to cause considerable delay. The reason for this is the manner in which synchronous calls work. The application blocks the client until the web service call returns. To overcome the necessity of having to wait for the web service response, we can call web services asynchronously. The asynchronous call mechanism does not need any additional functionality for the web service to handle it competently. The decision on whether to call synchronously or asynchronously belongs to the client.

Currently there are two methods of performing asynchronous calls:

1. CallBacks
2. WaitHandles

Here are a couple of web service web methods that we will be using in the demo. Two web methods, MyWebMethod and CreateXMLFile, are declared in the web service. MyWebMethod method takes a string parameter and concatenates "You speak " to it and returns the result. The CreateXMLFile method takes a string parameter and creates an XML file in the C://temp directory:

// [C# Code]
[WebMethod()]
public string MyWebMethod(string lang)
{
  System.Threading.Thread.Sleep(3000);
  return "You speak " + lang;
}

[SoapDocumentMethod(OneWay=true)]
[WebMethod()]
public void CreateXMLFile(string lang)
{
   // To set a 3 second thread sleep
   System.Threading.Thread.Sleep(3000);
         
   // Create an XMLDocument instance
   XmlDocument doc = new System.Xml.XmlDocument();

   // Load the Xml String into XmlDocument
   doc.LoadXml("<Root xmlns=\"http://CreateXMLFile\">
		<Resultxmlns=\"\">"+lang+"</Result></Root>");
         
   // Save the document
   doc.Save("C:\\temp\\MyFile1.xml");
}

Before we jump off to writing asynchronous calls, let us take a look at how the synchronous call is made so that we can better understand the asynchronous call mechanism.

Synchronous Call

// Create an instance of the WebService
localhost.MyAsyncWebService webServ = 
   		new localhost.MyAsyncWebService();

// Return the result string
strResult = webServ.MyWebMethod("English");

The synchronous call mechanism is pretty straightforward; all we would need to do would be to declare an instance of the web service. As the web service is running locally, we would need to append the string "localhost" to the web service name. Once the web service is declared, web methods can be called as demonstrated above. Now let us start writing asynchronous calls.

Asynchronous Call using an AsyncCallback

In this approach, we create a delegate which can be invoked during runtime when the results from the web service are returned. Here's how it works.

// Button Click event
private void AsyncCallUsingCallBackBtn_Click
	(object sender, System.EventArgs e)
{
   string mLangInput = "English";

   // Create an instance of the WebService
   localhost.MyAsyncWebService webServ = 
		new localhost.MyAsyncWebService();

   // Create a delegate to handle the callback
   AsyncCallback asyncCall = 
		new AsyncCallback(CallbackSampleMethod);

   // Make an Asynchronous Call by calling 
   // the Begin method of the proxy class
   webServ.BeginMyWebMethod(this.mLangInput, asyncCall, webServ);
			
   // Do some process while the web 
   // service is processing the request
   System.Threading.Thread.Sleep(10000);

}

// CallBack function
private void CallbackSampleMethod(IAsyncResult asyncResult)
{
   // Create an instance of the WebService
   localhost.MyAsyncWebService webServ = 
		(localhost.MyAsyncWebService)asyncResult.AsyncState;
						
   // Get the Result of the WebMethod by calling 
   // the end method of the proxy class
   mLangResult = webServ.EndMyWebMethod(asyncResult);

   // Display the results in a label
   Label1.Text = this.mLangResult;
}

In the Button Click event, the proxy's Begin<WebServiceMethod>(BeginMyWebMethod) web service is called by passing in the following parameters:

• WebMethod parameters (this.mLangInput)
• AsyncCallback(asyncCall)
• An instance of the web service(webServ)

The CallBack function should have an instance of the IAsyncResult instance as a parameter (see the above code). After the web service returns the results, then the Callback function is activated (CallbackSampleMethod). Results of the web service are obtained by calling the proxy's End<WebServiceMethod> (EndMyWebMethod).

Asynchronous Call using WaitHandle

This approach utilizes a different technique, in that we have a wait handle object. This object will wait until the web service returns. When the parent thread gets to the function WaitOne (or WaitAll or WaitOne), it waits for the web service to return. After the web service returns the results, then the parent thread process will continue.

string mLangInput = "English";

// Create an instance of the WebService
localhost.MyAsyncWebService webServ =  
new localhost.MyAsyncWebService();

// Create an IAsyncResult object to hold results
IAsyncResult asyncResult;


// Make an Asynchronous Call
asyncResult = webServ.BeginMyWebMethod
  (this.mLangInput, null, null);

// Do something while the WebService is doing its work
str1 = "Doing some work while the WebService is being called.";

// Call WaitHandle to wait for the web service method to return
WaitHandle wtHandle = asyncResult.AsyncWaitHandle;
wtHandle.WaitOne();

// Get the Result of the WebMethod (this occurs when 
// WebService finished processing)
mLangResult = webServ.EndMyWebMethod(asyncResult);

// Display the results in a label
Label1.Text = str1 + this.mLangResult;

This process uses the Begin<WebServiceMethod> (BeginMyWebMethod) and assigns the result to the IAsyncResult instance, passing in method parameters and null values for Callback and asyncState (as callback is not used). The WaitOne() method causes the thread to wait for the results from the web service. When the results from the web service are ready, then End<WebServiceMethod> (EndMyWebMethod) is called to retrieve the results.

Asynchronous Call (Fire and Forget)

Very often, there can arise certain situations where a web method does not return any value. Also, a process may need to be kicked off the web server without waiting for the results. We can better illustrate this with the help of the following example. We will create an XML file using the CreateXmlFile web method, passing in a value. Note: if there is any error while creating an XML file at the web service end, then the web application cannot be notified, as the results are not returned to the web app from the web service.

// WebService web method
using System.Web.Services.Protocols;

[SoapDocumentMethod(OneWay=true)]
[WebMethod()]
public void CreateXMLFile(string lang) //No return value
{
  //. . . . . . . . . . . 
}

Client Call:

string mLangsInput = "English";

// Create an instance of the WebService
localhost.MyAsyncWebService webServ = 
	new localhost.MyAsyncWebService();

// Make a Web Method Call to create an XMLFile
webServ.CreateXMLFile(mLangInput);

// Do some process while the web service is processing the request
System.Threading.Thread.Sleep(10000);

To support fire-and-forget method calls, web methods should have an attribute SoapDocumentMethod, with the OneWay attribute set to true. SoapDocumentMethod resides in the System.Web.Services.Protocols namespace; make sure that this namespace was used in the web service. Fire and forget methods cannot have any return values, as the client does not expect any results. When you use fire and forget web methods, it does not really matter whether you have chosen an asynchronous or synchronous process, as the parent thread does not wait for the results.

WaitHandle Object Methods

The WaitHandle object has three important methods; WaitOne, WaitAll, and WaitAny. Multiple calls can be made asynchronously to web services from a single parent thread. Here is an example:

// Declare two instances of Web Service
localhost.MyAsyncWebService webServ1 = 
	new localhost.MyAsyncWebService();
localhost.MyAsyncWebService webServ2 = 
	new localhost.MyAsyncWebService();

// Declare two instances of IAsyncResult
IAsyncResult asyncResult1;
IAsyncResult asyncResult2;

// Make  two Asynchronous Calls to Web Service
asyncResult1 = webServ1.BeginCreateXMLFile
	(this.mLangInput, null, null);
asyncResult2 = webServ2.BeginCreateXMLFile
	(this.mLangInput, null, null);

// Call WaitHandle to wait for the web service method to return
WaitHandle wtHandle = asyncResult.AsyncWaitHandle;
// Causes to Wait until both the calls are returned
wtHandle.WaitAll();  

// Causes to Wait until any of the calls to be returned
// wtHandleAny();

Here, two calls were made asynchronously to web services. The WaitAll() method causes the parent thread to wait for both (All) of the asynchronous calls to return before it can proceed. The WaitAny() method causes it to just wait for any (Any) asynchronous call to return. If only one asynchronous call is made, then WaitOne() is used. For more information on the WaitHandle object, look here at MSDN.

Callback Vs. WaitHandle

The choice of which approach to use is application-driven. If the application needs the results from the web service to be used in the later stages of the thread, then the WaitHandle is the best approach. For example, if the web service queries a database and retrieves a value that needs to be used in the parent process and then displays the result to the user, then WaitHandle should be used. We need the parent thread to stop processing at a certain stage so that we can use the results from the web service to do further computation and display the final results. Most web apps come under this scenario. In all other scenarios, we can use callback. Mostly Windows apps use this approach.

Conclusion

Asynchronous calls to web services will significantly enhance performance because they enable parallel processing of the parent thread and the web service call by using two separate threads. This will be very effective, especially if the web service method takes a long time to process, since it lets the parent thread continue while the web service is doing its own process.

Related Links

• Web Service Development Center
• "Introducing XML Web services"

---

Managing online business requires different skills and abilities than managing a business in the ‘real world.’ Customers can easily detect the size and determine the prestige of a business when they have the ability to walk in and take a look around. Not only do ‘real-world’ furnishings and location tell the customer what level of professionalism to expect, but "real world" personal encounters allow first impressions to be determined by how the business approaches its customer service. When a customer walks into a retail business just about anywhere in the world, that customer expects prompt and personal service, especially with regards to questions that they may have about products they wish to purchase.

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By Jayashree Pakhare (buzzle.com)

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