How Does Email Work?

Introduction

SonicSpider-managed domains use the email system provided by Enom.com. This system provides Pop and SMTP services for all of our customers that have their domains registered with us (via Enom.com) Following is a brief discussion of how this system works to help solve various problems that may occur from time to time.

Overview

Mail servers basically are  large databases connected to a "listener" that sits and waits for other mail servers to contact it and deliver mail. Each mail server "advertises" its address via addresses (name servers) and listens on either port 25 or 110. (smtp and pop respectively) Once it receives an email that is properly addressed to one of its mailboxes (defined by your email address) it stores the email and waits for you to request your mail. You have two ways to access your mail, either via a "web mail" interface or via an "email client" like Netscape, Outlook, Mozilla, Thunderbird, or Mac Mail (to name a few of the more popular email clients - there are others.) Once an email is read or retrieved it is stamped "read" and can be deleted. Both interfaces are viewing the SAME email box. They are not different places.

The System

Email is not a "guaranteed delivery system" and therefore there are times when an email just disappears into "byte heaven".  Despite that, it is generally very reliable. Basically, the system works by email "servers" contacting each other and passing your message.   The following description leaves some of the technical details out on purpose, in order to make it understandable.

First, the sending server extracts the "domain" from the recipient's  email address.  It then queries the assigned DNS server (Domain Name Server) for the MX record for that domain (This is the record that contains the address of your email server). If there is an MX record it now tries to contact the server described in that record using the SMTP protocol.  If a connection is made, the email address exists on that server, and all of the rules of the protocol are followed, then the email is transfered.  If not the email is "bounced" back to the sender.  Next is a fairly new wrinkle on the system - the spam and virus checkers that are built into modern mail servers.  Using the rules programmed by the email server administrators, each email is checked. In some cases a failed email is returned to the sender, but generally it is just "dropped" (i.e. byte heaven)

Though the system is fairly "simple" it is becoming more complex as the Internet and the abuses of the Internet grow. Because of this, the chances of an email NOT being delivered are becoming greater with each passing year.

A Review of Email Tools

Webmail allows you to view and work with your email box on any machine with a browser that is connected to the Internet. This is handy when traveling or when you cannot connect to your email via an "email client" It is important to understand that once you "read" an email from this view, it will not be "read" by a later request from the "email client". It will remain in the mailbox though, until you remove it.

An Email Client program (like Netscape, Outlook, Mozilla, Thunderbird, or Mac Mail) transfers your mail from the email server to your local machine. Once the the Email Client makes the transfer it then requests that the transferred emails be deleted from the server. This is generally a default setting and can be changed so that emails remain on the server. You must consult your documentation for your Email Client to determine the current setting. Generally, this is found under "Server Settings" and is a check box that indicates whether the emails should be removed or not.

Generally, all Email Clients have the same basic requirements. The only difference is in the screens and the sequence in which these settings are found. The primary settings are:

• Incoming Server Name: pop.yourdomain.com
• Outgoing Server Name: smtp.yourdomain.com
• User Name: <Your full email address>
• Password: <Configured in the Domain Manager>

That seems easy. Unfortunately, the writers of the Email Clients can sometimes take great pains to make those simple settings hard to find and set up.

Usually the biggest problems are either during the configuration or during the startup when users are most likely to do "odd" things in trying to get a handle on how to use their email. A couple of points need to be kept in mind when trying to troubleshoot these issues...

• Passwords are case sensitive.
• The User name must be the FULL email address.
• The Outgoing Server is often configured in a different place than the Incoming Server. In the Netscape/Mozilla/Thunderbird world this is at the bottom of the server listing after selecting "View Server Configuration".
• Passwords can be changed by SonicSpider in the Domain Manager, but they are hidden so we can never "see" your current password. Sometimes it is easier to change the password than try and remember what it  is.  Call to have your password "reset" if you have forgotten it.
  
• Once an email is "read" in webmail the Email Client will NOT upload that email. The user must go to their webmail and "forward" that email to themselves. This will make it a "new and unread" email.

For the Technically Inclined

The following information can get very technical. The basics are that SMTP is the basic system by which mail is transferred from your client email program to your email server and then passed on to the target email server that serves the address to which you sent the email. POP is the system for "getting" that email from your server. If that is too simple for you.. read on...

POP3 (Post Office Protocol 3) is the most recent version of a standard protocol for receiving e-mail. POP3 is a client/server protocol in which e-mail is received and held for you by your Internet server. Periodically, you (or your client e-mail receiver) check your mail-box on the server and download any mail, probably using POP3. This standard protocol is built into most popular e-mail products, such as Eudora and Outlook Express. It's also built into the Netscape and Microsoft Internet Explorer browsers.

POP3 is designed to delete mail on the server as soon as the user has downloaded it. However, some implementations allow users or an administrator to specify that mail be saved for some period of time. POP can be thought of as a "store-and-forward" service.

An alternative protocol is Internet Message Access Protocol (IMAP). IMAP provides the user more capabilities for retaining e-mail on the server and for organizing it in folders on the server. IMAP can be thought of as a remote file server.

POP and IMAP deal with the receiving of e-mail and are not to be confused with the Simple Mail Transfer Protocol (SMTP), a protocol for transferring e-mail across the Internet. You send e-mail with SMTP and a mail handler receives it on your recipient's behalf. Then the mail is read using POP or IMAP.

The conventional port number for POP3 is 110. For the technically inclined a full specification for POP3 can be found at:

SMTP is a relatively simple, text-based protocol, where one or more recipients of a message are specified (and in most cases verified to exist) and then the message text is transferred. It is quite easy to test a SMTP server using the telnet program. SMTP uses TCP port 25. To determine the SMTP server for a given domain name, the MX (Mail eXchange) DNS record is used. To test if your email server is online, open a console or terminal window and at the prompt type:

SMTP started becoming widely used in the early 1980s. At the time, it was a complement to UUCP 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.

Sendmail was one of the first (if not the first) mail transfer agents to implement SMTP. As of 2001 there are at least 50 programs that implement SMTP as a client (sender of messages) or a server (receiver of messages). Some other popular SMTP server programs include Philip Hazel's exim, IBM's Postfix, D. J. Bernstein's Qmail, and Microsoft Exchange Server.

Since this protocol started out as purely ASCII text-based, it did not deal well with binary files. Standards such as MIME were developed to encode binary files for transfer through SMTP. Today, most SMTP servers support the 8BITMIME extension, permitting binary files to be transmitted almost as easily as plain text.

SMTP is a "push" protocol that does not allow one to "pull" messages from a remote server on demand. To do this a mail client must use POP3 or IMAP. Another SMTP server can trigger a delivery in SMTP using ETRN.

The conventional port number for SMTP is 25. For the technically inclined a full specification for SMTP can be found at:

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Posted by Melanie Moore on January 13, 2007 1:25:00 PM PST #